Fine polymer particles having heterogeneous phase structure

ABSTRACT

Latex polymer of fine particles having a heterogeneous phase structure which comprises a core of a polymer having repeating units derived from a conjugated diene monomer and a shell of a polymer having repeating units derived from at least one ethylenically unsaturated monomer carrying an active methylene group; a silver halide photographic light-sensitive material comprises a core/shell latex polymer whose shell consists of a polymer having repeating units of an ethylenically unsaturated monomer represented by the formula: CH 2  ═C(R 1 )--L--X (wherein R 1  represents H, alkyl or halogen, L represents a single bond or a bivalent coupling group, X represents an active methylene group, provided that L is bonded to X in the form of alkylene; and a method for forming images on a silver halide light-sensitive material which comprises exposing the material which comprises at least one light-sensitive silver halide emulsion layer and at least one hydrophilic colloidal layer either of which comprises a latex polymer having active methylene groups and developing the exposed material with a developer which comprises a dihydroxybenzene developing agent and an auxiliary developing agent showing superadditivity, the pH increase observed when adding 0.1 mole/l developer of NaOH to the developer ≦0.25; 9.5≦ initial pH of the developer ≦11.0; the amount of the developer supplemented ≦225 ml/ml 2 .

This is a divisional of application Ser. No. 08/960,123 filed Oct. 27,1997 and now U.S. Pat. No. 5,804,357, which is a continuation ofapplication Ser. No. 08/569,500 filed Dec. 8, 1995, now abandoned, thedisclosure of which is incorporated herein by reference.

TITLE OF THE INVENTION

Fine Polymer Particles Having Heterogeneous Phase Structure, SilverHalide Photographic Light-Sensitive Material Containing the Fine PolymerParticles and Image-Forming Method.

BACKGROUND OF THE INVENTION

The present invention relates to a latex polymer of fine particlesuseful in applications such as silver halide photographiclight-sensitive materials, paints and varnishes and adhesives.

The present invention also relates to a silver halide photographiclight-sensitive material and more specifically to a silver halidephotographic light-sensitive material containing a novel latex polymer.More specifically, the present invention relates to a silver halidephotographic light-sensitive material improved in physical properties offilms without impairing photographic properties, through the use of thelatex polymer.

The present invention further relates to a method for forming images ona silver halide photographic light-sensitive material which permits theformation of high contrast images at a pH of less than 11.0 and moreparticularly to an image-forming method which requires only a smallamount of developer to be supplemented.

As the active methylene group can react with amino groups, isocyanatesand melamines to form covalent bonds, there have long been proposedvarious applications of polymers having reactive groups on the sidechains thereof which are formed through homopolymerization ofethylenically unsaturated monomers carrying active methylene groups orcopolymerization thereof with various other ethylenically unsaturatedmonomers.

On the one hand, gelatin is generally and widely used as a binder in thehydrophilic colloidal layer constituting the photographiclight-sensitive material. Gelatin is a binder having quite excellentcharacteristic properties. For instance, it has high swelling andgelling abilities and can easily be crosslinked with a variety offilm-hardening agent.

On the other hand, if gelatin is used as an ingredient for forming thehydrophilic colloidal layer, it can not always impart satisfactoryphysical properties to the resulting film. For instance, it suffers fromproblems such as deformation due to plastication of the film under highhumidity conditions, extension of the film due to absorption of moistureor brittleness of the film under low humidity conditions.

In order to eliminate such drawbacks of the gelatin film, there havebeen proposed many attempts to improve of, for instance, the dimensionalstability against humidity, scratch resistance, brittleness and dryingcharacteristics of hydrophilic colloidal films by incorporating a latexpolymer into the hydrophilic colloidal layers such as silver halideemulsion layers, protective layers, backing layers and intermediatelayers.

For instance, U.S. Pat. Nos. 2,763,625 and 2,852,382, JapaneseUn-Examined Patent Publication (hereinafter referred to as "J.P. KOKAI")Nos. Sho 62-115152, Hei 5-66512 and Hei 5-80449 and Japanese ExaminedPatent Publication (hereinafter referred to as "J.P. KOKOKU") Nos. Sho60-15935, Hei 4-64058 and Hei 5-45014 disclose the use of latexpolymeres derived from a variety of monomers represented by alkylacrylates and alkyl methacrylate in gelatin-containing hydrophiliccolloidal layers.

The use of the latex of this type is effective in the improvement ofsome characteristic properties of the gelatin film, but the resultinggelatin film is insufficient in the strength under, in particular, highhumidity conditions or water-containing state. Incidentally, it has beenknown that such problems can be solved by incorporating, into the latex,active methylene groups reactive with gelatin or coexistingfilm-hardening agents, through copolymerization.

For instance, J.P. KOKOKU Nos. Sho 45-5819 and Sho 46-22507 and J.P.KOKAI No. Sho 50-73625 disclose that, in photographic light-sensitivematerials, the wear resistance and hardness of a latex-containinggelatin film (in particular, these properties thereof in wet conditions)are improved by incorporating, into a gelatin film, a latex polymerobtained by copolymerizing a monomer carrying an active methylene groupsuch as 2-acetoacetoxyethyl methacrylate or 2-cyanoacetoxyethylmethacrylate with a monomer such as an alkyl acrylate.

However, more than a certain amount of the active methylene-containingmonomer must be copolymerized for preparing the foregoing latex used forimproving the wear resistance and hardness of the gelatin film to adesired level.

Moreover, if the ratio of the latex to gelatin increases or the absolutequantity of gelatin is reduced, the strength of the resulting gelatinfilm in a wet state is considerably reduced. As a result, the amount ofthe active methylene-containing monomer to be copolymerized must befurther increased or any gelatin film having a desired strength cannotbe obtained by simply increasing the amount of the activemethylene-containing monomer.

The reduction in the coated amount of gelatin has become an importantsubject in recent photographic light-sensitive materials, from theviewpoint of obtaining high quality images, requirements for highlyimproved physical properties of films and speeding up of the processingof the materials. In the field of phototype process, for instance, therehas intensively been desired for the improvement in the dimensionalstability of the photographic light-sensitive material by reducing theamount of gelatin to be used in the material or for the reduction of theamount of processing solutions to be supplemented by reducing the amountof the processing solutions carried over by the material duringprocessing.

Therefore, these films having low gelatin contents and gelatin filmscomprising a large amount of such a latex suffer from problems such thatthe film strength is sometimes insufficiently improved through theincorporation of a latex conventionally obtained by simplycopolymerizing an active methylene-containing monomer and that theproduction cost of such a latex polymer increases due to the use of alarge amount of an active methylene-containing monomer having arelatively complicated structure. Accordingly, there has been desiredfor further improvement.

Moreover, J.P. KOKAI No. Hei 5-295302, European Patent Laid-Open(hereinafter referred to as "EPLO") No. 501666, InternationalUn-Examined Patent Publication (hereinafter referred to as "KOHYO") No.93-16133 disclose that copolymers of active methylene-containingmonomers exhibit excellent properties as latexes for use in paints andvarnishes such as water resistance, resistance to saline solutions andresistance to alkalis and J.P. KOKAI Nos. Hei 4-253784, Hei 5-194914 andHei 5-287248, EPLO No. 573142 or the like disclose that latexcopolymeres of active methylene-containing monomers exhibit excellentproperties as latexes for use in adhesives such as adhesion strength andwater resistance.

Toshihiko NAKAMICHI, Coloring Materials, 1992, 65, pp. 511-525 disclosesthat the copolymers of active methylene-containing monomers formthree-dimensionally crosslinked films if they are used in combinationwith various additives and it can be appreciated that the effects of thecopolymers of active methylene-containing monomers on the foregoingfields of paints and varnishes and adhesives are accomplished by thecrosslinking reaction.

In these fields, however, there has also been desired for thedevelopment of materials which can impart more excellent properties tothe resulting product while using the same amount of an activemethylene-containing monomer, from both quality and economicalstandpoints.

On the other hand, as examples of latex polymeres having core/shell dualstructures, J.P. KOKAI No. Sho 58-42044 discloses silver halide colorphotographic light-sensitive materials comprising core/shell latexeswhose shell portion consists of a polymer containing coupler unitscapable of forming a dye through coupling with an oxidized developingagent and also discloses pivaloylacetanilide type or benzoylacetanilidetype couplers as specific examples of yellow couplers.

However, the core/shell latex polymeres disclosed in this patent sufferfrom the following problems:

(i) The rate of the core comprising a non-dye-forming monomer is verylow (at most 10%, among the compounds listed). Therefore, theconcentration of the active methylene moieties on the shell side throughthe formation of a core/shell structure does not ensure the foregoingvarious merits so much. The foregoing rate of the core portion is quiteinsufficient while taking into consideration the fact that it iseffective for, for instance, reducing the thickness of light-sensitivematerials to increase the content of coupler monomer units as high aspossible, in the field of polymer couplers.

(ii) The reactivity of a compound having an active methylene structurewhich is sterically complicated beyond a certain level such aspivaloylacetoanilide or benzoylacetoanilide is not necessarilysufficient and must be further improved from the viewpoint of, forinstance, the effect of improving the strength of gelatin films.

In addition, this patent does not disclose the use of a conjugated dienemonomer as a material for the core particles and the usefulness thereof.

On the other hand, in the field of recent graphic arts, the printingprocess is apt to be complicated as the color printing has widely beenemployed. There has been increased a demand for reducing the appointeddate of delivery since much importance has been attracted to theimmediate availability of information.

In compliance with such a demand, there has been proposed a method inwhich a film for plate-making by printing is processed with a developerundergoing only a small variation in pH to stabilize the developingprocess and to thus stabilize the precision of the overall plate-makingprocess. It has been known that any change in the quality of photographscan be reduced by minimizing the variation in pH of the developer. Forinstance, J.P. KOKOKU No. Hei 3-5730 discloses a method for stabilizingthe quality of photographs by improving the buffering ability of thedeveloper.

However, if the buffering ability of the developer is improved byincreasing a salt concentration, the hydrophilic colloidal layer is notsufficiently swollen and accordingly, this process does not providephotographs showing high contrast. Moreover, in the light-sensitivematerial whose hydrophilic colloidal layer comprises a dye or a pigment,a problem arises, such as severe remaining color stain.

It has been known that the developer is supplied in the form of a solidprocessing agent. For instance, J.P. KOKAI No. Sho 61-259921 discloses amethod for improving the stability of a solid processing agent as adeveloper.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a latex polymercomprising an active methylene monomer having a novel structure.

Another object of the present invention is to provide a latex polymereffectively used in gelatin/latex composite films excellent in the filmstrength, paints and varnishes excellent in water resistance andadhesion strength and adhesive compositions.

A still another object of the present invention is to provide a silverhalide photographic light-sensitive material comprising a novel latexpolymer.

A further object of the present invention is to provide a silver halidephotographic light-sensitive material which permits the solution of theproblems concerning strength and brittleness of the gelatin film throughthe use of the foregoing latex without impairing the photographicproperties of the material.

A still further object of the present invention is to provide a silverhalide photographic light-sensitive material which permits the formationof a film having sufficient strength even if the amount of gelatin usedis low, which is excellent in the dimensional stability and which alsopermits the reduction of the amounts of processing solutions to besupplemented during processing the materials.

It is also an object of the present invention to provide a method forforming images on a silver halide monochromatic photographiclight-sensitive material, which permits the formation of a negativeimage having sufficiently high contrast even by a stable developerhaving a pH of less than 11.0, which can provide photographs showingonly a small quality change although the amount of the developersupplemented is small and which can always provide photographs showingstable quality.

According to a first aspect of the present invention, there is provideda latex polymer of fine particles having a heterogeneous phase structurewhich comprises a core consisting of a polymer having repeating unitsderived from a conjugated diene monomer and a shell consisting of apolymer having repeating units derived from at least one ethylenicallyunsaturated monomer carrying an active methylene group.

In a preferred embodiment of the latex polymer of fine particles havinga heterogeneous phase structure according to the first aspect of thepresent invention, the weight ratio of the core polymer to the shellpolymer ranges from 20/80 to 95/5. In another preferred embodiment ofthe latex polymer of fine particles having a heterogeneous phasestructure of the present invention, the ethylenically unsaturatedmonomer carrying an active methylene group is a monomer represented bythe following general formula (I):

    CH.sub.2 ═C(R.sup.1)--L--X

wherein R¹ represents a hydrogen atom, an alkyl group having 1 to 4carbon atoms or a halogen atom; L represents a single bond or a bivalentcoupling group; X represents an active methylene group selected from thegroup consisting of R² COCH₂ COO--, NC--CH₂ COO--, R² COCH₂ CO--,NC--CH₂ CO-- (wherein R² represents a substituted or unsubstituted alkylgroup having 1 to 12 carbon atoms, a substituted or unsubstituted arylor aryloxy group having 6 to 20 carbon atoms, an alkoxy group having 1to 12 carbon atoms, an amino group or a substituted amino group having 1to 12 carbon atoms) and R⁹ --CO--CH₂ CON(R⁶)-- (wherein R⁶ represents ahydrogen atom or a substituted or unsubstituted alkyl group having 1 to6 carbon atoms and R⁹ represents a substituted or unsubstituted, primaryor secondary alkyl group having 1 to 12 carbon atoms, an alkoxy grouphaving 1 to 12 carbon atoms, an amino group or a substituted amino grouphaving 1 to 12 carbon atoms), provided that if L is not a single bond, Lis bonded to X in the form of an alkylene, aralkylene or arylene.

According to a second aspect of the present invention, there is alsoprovided a silver halide photographic light-sensitive materialcomprising a core/shell latex polymer whose shell consists of a polymerhaving repeating units derived from an ethylenically unsaturated monomerrepresented by the foregoing general formula (I).

According to a third aspect of the present invention, there is alsoprovided a method for forming images on a silver halide monochromaticphotographic light-sensitive material which comprises exposing, tolight, a silver halide photographic light-sensitive material comprising,on the same surface of a substrate, at least one light-sensitive silverhalide emulsion layer and at least one protective layer, and thendeveloping the exposed light-sensitive material with a developer,wherein the silver halide emulsion layer and/or at least one of otherhydrophilic colloidal layers comprise a latex polymer having activemethylene groups; the developer comprises a dihydroxybenzene typedeveloping agent and an auxiliary developing agent showingsuperadditivity; the pH increase observed when sodium hydroxide is addedto the developer in an amount of 0.1 mole per liter of the developer isnot more than 0.25; the initial pH value of the developer ranges from9.5 to 11.0; and the amount of the developer supplemented is not morethan 225 ml/m².

In the specification and the claims of the present application, thewords "latex polymer" have the same meaning as "polymer latex".

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an electron micrograph of the polymer P-17 of the presentinvention.

FIG. 2 is an electron micrograph of the polymer P-19 of the presentinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention will hereinafter be described in more detail.

First of all, the polymer latex of fine particles of the presentinvention will hereinafter be described in more detail.

The latex polymer of the present invention is one having a core/shellheterogeneous phase structure and the core consists of a polymer havingrepeating units derived from a conjugated diene monomer.

Examples of preferred monomers having conjugated diene structuresinclude 1,3-butadiene, isoprene, 1,3-pentadiene, 2-ethyl-1,3-butadiene,2-n-propyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene,2-methyl-1,3-pentadiene, 1-phenyl-1,3-butadiene,1-α-naphthyl-1,3-butadiene, 1-β-naphthyl-1,3-butadiene,2-chloro-1,3-butadiene, 1-bromo-1,3-butadiene, 1-chlorobutadiene,2-fluoro-1,3-butadiene, 2,3-dichloro-1,3-butadiene,1,1,2-trichloro-1,3-butadiene and 2-cyano-1,3-butadiene. Among these,particularly preferred are 1,3-butadiene, isoprene and2-chloro-1,3-butadiene.

Moreover, the polymer constituting the core of the latex of the presentinvention may be a copolymer of the foregoing conjugated diene monomerwith other monomers. Examples of such other monomers include ethylene,propylene, 1-butene, isobutene, styrene, α-methylstyrene,divinylbenzene, vinyl ketone, monoethylenically unsaturated hydrocarbon(alkene) esters of aliphatic acids (such as vinyl acetate and allylacetate), esters of ethylenically unsaturated mono- or dicarboxylicacids (such as methyl methacrylate, ethyl methacrylate, n-butylmethacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, benzylmethacrylate, n-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate,t-butyl methacrylate, dodecyl methacrylate, 2-hydroxyethyl acrylate,2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate and ethyleneglycol dimethacrylate), amides of ethylenically unsaturated mono- ordicarboxylic acids (such as t-butyl acrylamide and t-butylmethacrylamide) and monoethylenically unsaturated compounds (such asacrylonitrile and methacrylonitrile).

Among these, particularly preferred are ethylene, propylene, styrene,α-methylstyrene, esters of (meth)acrylic acids and (meth)acrylonitriles.

The foregoing monomers having conjugated diene structures and othercopolymerizable monomers may, respectively, be used alone or incombination.

The unsaturated structures introduced into the core polymer through thepolymerization of the monomer having a conjugated diene structure maycomprise, as has been well known in this art, cis-1,4-bonds,trans-1,4-bonds or trans-1,2-bonds.

As has been described above, the core polymer may be a homopolymerderived from a monomer having a diene structure or a copolymer thereofwith other hydrophobic monomer. In case of copolymers, they may beso-called random copolymers obtained by copolymerizing these monomers inany ratio or block copolymers.

Polymers of such conjugated diene monomers and methods for synthesizingthe same are detailed in, for instance, "Gosei Kobunshi (SyntheticPolymers) II", 1975, pp. 171-308, edited by Shunsuke MURAHASHI et al.,Published by Asakura Shoten.

Preferred specific examples of the foregoing core polymers arestyrene-butadiene copolymers (in general referred to as "SBR" anddivided into solution polymerized SBR's and emulsion polymerized SBR's;examples of solution polymerized SBR's include random polymers as wellas the foregoing block copolymer such as butadiene-styrene blockcopolymers and styrene-butadiene-styrene block copolymers), butadienehomopolymers (such as rubbers of cis-1,4-butadiene, trans-1,2-butadieneor those comprising these monomers and/or trans-1,4-butadienestructures), isoprene homopolymers (which may have the same stericstructures as described above in connection with the butadienepolymers), styrene-isoprene copolymers (random and block copolymers),ethylene-propylene-diene copolymers (examples of diene monomers may be1,4-hexadiene, dicyclopentadiene and ethylidene norbornene),acrylonitrile-butadiene copolymers, chloroprene copolymers,isobutylene-isoprene copolymers, butadiene-acrylic acid ester copolymers(examples of acrylates are ethyl acrylate and butyl acrylate) andbutadiene-acrylic acid ester-acrylonitrile copolymers (the sameacrylates listed above may be used as the acrylate components).

The glass transition temperature (Tg) of these core polymers is ingeneral not more than 50° C., in particular, not more than 20° C.

The content of the conjugated diene monomer component present in thecore polymer is not limited to a specific range, but preferably rangesfrom 10 to 100% by weight.

In particularly preferred embodiment, the core polymer is in the form ofa dispersion (latex) of a homopolymer (such as those of butadiene andisoprene) derived from a monomer having a diene structure or a copolymerthereof (such as the SBR's listed above), which is prepared by theemulsion polymerization.

In such a dispersion, the core polymer is dispersed therein in the formof fine particles. It is not preferred to use such a dispersion ofparticles having an extremely large particle size since the particlesize of the polymer greatly affects physical properties of the filmprepared after mixing with gelatin, the dispersion stability of theparticles per se and the film-forming properties thereof.

Furthermore, the core constituting the latex of the present invention isspecifically a polymer consisting of repeating units derived from one orat least two polymerizable monomers selected from various kinds ofethylenically unsaturated monomers, in addition to the foregoingconjugated diene monomers.

Such monomers usable herein may be acrylic acid esters, methacrylic acidesters, vinyl esters, olefins, dienes, acrylamides, methacrylamides,vinyl ethers, dienes and other various ethylenically unsaturatedmonomers and it is also preferred to use monomers having at least twoethylenically unsaturated groups.

More specifically, examples of acrylic acid esters are methyl acrylate,ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate,isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, amylacrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate,tert-octyl acrylate, 2-chloroethyl acrylate, 2-bromoethyl acrylate,4-chlorobutyl acrylate, cyanoethyl acrylate, 2-acetoxyethyl acrylate,dimethylaminoethyl acrylate, benzyl acrylate, methoxybenzyl acrylate,2-chlorocyclohexyl acrylate, cyclohexyl acrylate, furfuryl acrylate,tetrahydrofurfuryl acrylate, phenyl acrylate, 5-hydroxypentyl acrylate,2,2-dimethyl-3-hydroxypropyl acrylate, 2-methoxyethyl acrylate,3-methoxybutyl acrylate, 2-ethoxyethyl acrylate, 2-iso-propoxy acrylate,2-butoxyethyl acrylate, 2-(2-methoxyethoxy)ethyl acrylate,2-(2-butoxyethoxy) ethyl acrylate, ω-methoxypolyethylene glycol acrylate(added molar amount n=9), 1-bromo-2-methoxyethyl acrylate and1,1-dichloro-2-ethoxyethyl acrylate.

Specific examples of methacrylic acid esters are methyl methacrylate,ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate,n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate,tert-butyl methacrylate, amyl methacrylate, hexyl methacrylate,cyclohexyl methacrylate, benzyl methacrylate, chlorobenzyl methacrylate,octyl methacrylate, stearyl methacrylate, N-ethyl-N-phenylaminoethylmethacrylate, 2-(3-phenylpropyloxy)ethyl methacrylate,dimethylaminophenoxyethyl methacrylate, furfuryl methacrylate,tetrahydrofurfuryl methacrylate, phenyl methacrylate, cresylmethacrylate, naphthyl methacrylate, 2-hydroxyethyl methacrylate,4-hydroxybutyl methacrylate, triethylene glycol monomethacrylate,dipropylene glycol monomethacrylate, 2-methoxyethyl methacrylate,3-methoxybutyl methacrylate, 2-acetoxyethyl methacrylate, 2-ethoxyethylmethacrylate, 2-isopropoxyethyl methacrylate, 2-butoxyethylmethacrylate, 2-(2-methoxyethoxy)ethyl methacrylate,2-(2-butoxyethoxy)ethyl methacrylate and allyl methacrylate.

Examples of vinyl esters are vinyl acetate, vinyl propionate, vinylbutyrate, vinyl isobutyrate, vinyl caproate, vinyl chloroacetate, vinylmethoxyacetate, vinyl phenylacetate, vinyl benzoate and vinylsalicylate.

In addition to the foregoing monomers, examples of monomers usable forpreparing the core polymers further include acrylamides such asacrylamide, ethyl acrylamide, t-butyl acrylamide, cyclohexyl acrylamide,benzyl acrylamide, hydroxymethyl acrylamide, phenyl acrylamide, dimethylacrylamide, diethyl acrylamide and diacetone acrylamide; methacrylamidessuch as methacrylamide, ethyl mathacrylamide, t-butyl methacrylamide,benzyl methacrylamide, hydroxymethyl methacrylamide, phenylmethacrylamide and dimethyl methacrylamide; olefins such as ethylene,propylene, 1-butene, 1-pentene, vinyl chloride and vinylidene chloride;styrenes such as styrene, methylstyrene, ethylstyrene,chloromethylstyrene, methoxystyrene, acetoxystyrene, chlorostyrene,dichlorostyrene, bromostyrene and methyl vinylbenzoate; vinyl etherssuch as methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether andmethoxyethyl vinyl ether; and other monomers such as butyl crotonate,hexyl crotonate, dimethyl itaconate, dimethyl maleate, dibutyl maleate,diethyl fumarate, dimethyl fumarate, methyl vinyl ketone, phenyl vinylketone, methoxyethyl vinyl ketone, N-vinyl pyrrolidone, acrylonitrile,methacrylonitrile, methylene malonitrile, vinylidene chloride, acrylicacid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride,vinylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid andstyrenesulfonic acid.

Moreover, monomers each carrying at least two copolymerizableethylenically unsaturated groups may likewise be used to prepare thecore of the latex of the present invention.

Examples of such monomers are divinylbenzene, ethylene glycoldiacrylate, ethylene glycol dimethacrylate, diethylene glycoldiacrylate, diethylene glycol dimethacrylate, triethylene glycoldiacrylate, triethylene glycol dimethacrylate, trivinylcyclohexane,trimethylolpropane triacrylate, trimethylolpropane trimethacrylate,pentaerythritol triacrylate, pentaerythritol trimethacrylate,pentaerythritol tetraacrylate and pentaerythritol tetramethacrylate.

The foregoing monomers may be used alone or at least two of them may becopolymerized. Among the monomers listed above, preferably used areacrylic acid esters, methacrylic acid esters, vinyl esters, conjugateddienes, styrenes and monomers carrying at least two ethylenicallyunsaturated groups, from the viewpoint of easiness of polymerization andeasy formation of the core/shell structure.

In a particularly preferred embodiment, the core polymer is prepared bythe emulsion polymerization and is present in an aqueous medium in theform of a dispersion (latex) of fine particles.

In such a dispersion, the core polymer is dispersed therein in the formof fine particles.

It is not preferred to use such a dispersion having an extremely largeparticle size since the particle size of the polymer greatly affectsphysical properties of the film prepared after mixing with gelatin, thedispersion stability of the particles per se and the film-formingproperties thereof.

As has been discussed above, the number-average particle size of thecore polymer is not more than 1.0 μm, preferably not more than 0.7 μmand particularly preferably not more than 0.5 μm. Moreover, it ispreferably not less than 0.00001 μm.

The shell portion of the core/shell latex of the present invention willhereinafter be described in detail.

The shell portion consists of a polymer having repeating units derivedfrom an ethylenically unsaturated monomer (active ethylene monomer)carrying at least one kind of active methylene group.

In the present invention, the active methylene monomer is a monomerrepresented by the following general formula (I):

    CH.sub.2 ═C(R.sup.1)--L--X

wherein R¹ represents a hydrogen atom, an alkyl group having 1 to 4carbon atoms or a halogen atom; L represents a single bond or a bivalentcoupling group; X represents an active methylene group selected from thegroup consisting of R² COCH₂ COO--, NC--CH₂ COO--, R² COCH₂ CO--,NC--CH₂ CO-- (wherein R² represents a substituted or unsubstituted alkylgroup having 1 to 12 carbon atoms, a substituted or unsubstituted arylor aryloxy group having 6 to 20 carbon atoms, an alkoxy group having 1to 12 carbon atoms, an amino group or a substituted amino group having 1to 12 carbon atoms) and R⁹ --CO--CH₂ CON(R⁶)-- (wherein R⁶ represents ahydrogen atom or a substituted or unsubstituted alkyl group having 1 to6 carbon atoms and R⁹ represents a substituted or unsubstituted, primaryor secondary alkyl group having 1 to 12 carbon atoms, an alkoxy grouphaving 1 to 12 carbon atoms, an amino group or a substituted amino grouphaving 1 to 12 carbon atoms), provided that if L is not a single bond, Lis bonded to X in the form of an alkylene, aralkylene or arylene.

The substituent R¹ preferably represents a hydrogen atom, a methyl,ethyl, n-propyl or n-butyl group or a chlorine or bromine atom, inparticular, a hydrogen atom, a methyl group or a chlorine atom.

L represents a single bond or a bivalent coupling group such as acoupling group represented by the following formula:

    --(L.sup.1)m--(L.sup.2)n--

wherein L¹ represents --CON(R³)-- (R³ represents a hydrogen atom, analkyl group having 1 to 4 carbon atoms or a substituted alkyl grouphaving 1 to 6 carbon atoms), --COO--, --NHCO--, --OCO--, or a grouprepresented by the following formula: ##STR1## (R⁴ and R⁵ eachindependently represents a hydrogen atom, a hydroxyl group, a halogenatom or a substituted or unsubstituted alkyl, alkoxy, acyloxy or aryloxygroup and R³ is identical to that defined above); L² represents acoupling group connecting the group L¹ to X; m is 0 or 1 and n is 0or 1. The coupling groups represented by L² are, for instance, thoserepresented by the following general formula:

    --X.sup.1 --(J.sup.1 --X.sup.2)p--(J.sup.2 --X.sup.3)q--(J.sup.3 --X.sup.4)r--

Wherein J¹, J² and J³ may be the same or different and each represents--CO--, --SO₂ --, --CON(R⁶)-- (R⁶ represents a hydrogen atom, an alkylgroup (having 1 to 6 carbon atoms), a substituted alkyl group (having 1to 6 carbon atoms)), --SO₂ N(R⁶)-- (R⁶ is identical to that definedabove), --N(R⁶)--R⁷ -- (R⁶ is identical to that defined above and R⁷ isan alkylene group having 1 to about 4 carbon atoms), --N(R⁶)--R⁷--N(R⁸)-- (R⁶ and R⁷ are identical to those defined above and R⁸represents a hydrogen atom, an alkyl group (having 1 to 6 carbon atoms)or a substituted alkyl group (having 1 to 6 carbon atoms)), --O--,--S--, --N(R⁶)--CO--N(R⁸)-- (R⁶ and R⁸ are identical to those definedabove respectively), --N(R⁶)--SO₂ --N(R⁸)-- (R⁶ and R⁸ are identical tothose defined above respectively), --COO--, --OCO--, --N(R⁶)CO₂ -- (R⁶is identical to that defined above) or --N(R⁶)CO-- (R⁶ is identical tothat defined above); p, q and r each represents 0 or 1; X¹, X², X³ andX⁴ may be the same or different and each represents a substituted orunsubstituted alkylene group having 1 to 10 carbon atoms, an aralkylenegroup having 7 to 20 carbon atoms or a phenylene group having 6 to 20carbon atoms and the alkylene group may be linear or branched ones.Specific examples of the alkylene groups include methylene,methylmethylene, dimethylmethylene, methoxymethylene, dimethylene,trimethylene, tetramethylene, pentamethylene, hexamethylene anddecylmethylene; the aralkylene group includes, for instance,benzylidene; and the phenylene group includes, for instance,p-phenylene, m-phenylene, methylphenylene and chlorophenylene groups.

X represents a monovalent group carrying an active methylene group suchas R² COCH₂ COO--, NCCH₂ COO--, R² COCH₂ CO--, NCCH₂ CO--, R⁹ --CO--CH₂CON(R⁶)--.

In this respect, R⁶ is identical to that defined above; R² is asubstituted or unsubstituted alkyl group having 1 to 12 carbon atoms(such as methyl, ethyl, n-propyl, n-butyl, t-butyl, n-nonyl,2-methoxyethyl, 4-phenoxybutyl, benzyl and 2-methanesulfonamidoethylgroups), a substituted or unsubstituted aryl group having 6 to 20 carbonatoms (such as phenyl, p-methylphenyl, p-methoxyphenyl ando-chlorophenyl groups), an alkoxy group having 1 to 12 carbon atoms(such as methoxy, ethoxy, methoxyethoxy and n-butoxy groups), acycloalkyloxy group (such as cyclohexyloxy group), a substituted orunsubstituted aryloxy group having 6 to 20 carbon atoms (such asphenoxy, p-methylphenoxy, o-chlorophenoxy and p-cyanophenoxyl groups),an amino group or a substituted amino group hating 1 to 12 carbon atoms(such as methylamino, ethylamino, dimethylamino, butylamino anddichlorophenylamino groups).

Among the foregoing substituents, particularly preferred R² groups aresubstituted or unsubstituted, primary or secondary alkyl groups having 1to 12 carbon atoms.

R⁹ represents a substituted or unsubstituted, primary or secondary alkylgroup having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbonatoms, an amino group or a substituted amino group having 1 to 12 carbonatoms. Specific examples thereof are those listed above in connectionwith the substituent R². Particularly preferred R⁹ groups aresubstituted or unsubstituted, primary or secondary alkyl groups having 1to 12 carbon atoms.

Among these active methylene groups represented by X and listed above,those showing particularly preferred effects in the present inventionare R² COCH₂ COO--, NCCH₂ COO--, R² COCH₂ CO-- and NCCH₂ CO--.

Specific examples of the monomers carrying active methylene groups fromwhich the repeating units constituting the shell of the latex of thepresent invention will be listed below, but the present invention is notrestricted to these specific examples.

M-1 2-acetoacetoxyethyl methacrylate;

M-2 2-acetoacetoxyethyl acrylate;

M-3 2-acetoacetoxypropyl methacrylate;

M-4 2-acetoacetoxypropyl acrylate;

M-5 2-acetoacetamidoethyl methacrylate;

M-6 2-acetoacetamidoethyl acrylate;

M-7 2-cyanoacetoxyethyl methacrylate;

M-8 2-cyanoacetoxyethyl acrylate;

M-9 N-(2-cyanoacetoxyethyl)acrylamide

M-10 2-propionylacetoxyethyl acrylate

M-11 N-(2-propionylacetoxyethyl)methacrylamide

M-12 N-4-(acetoacetoxybenzyl)phenyl acrylamide

M-13 ethylacryloyl acetate

M-14 acryloylmethyl acetate

M-15 N-methacryloyloxymethyl acetoacetamide

M-16 ethylmethacryloyl acetoacetate

M-17 N-allylcyanoacetamide

M-18 2-cyanoacetylethyl acrylate

M-19 N-(2-methacryloyloxymethyl)cyanoacetamide

M-20 p-(2-acetoacetyl)ethylstyrene

M-21 4-acetoacetyl-1-methacryloyl piperazine

M-22 ethyl-α-acetoacetoxy methacrylate

M-23 N-butyl-N-acryloyloxyethyl acetoacetamide

M-24 p-(2-acetoacetoxy)ethylstyrene

The polymer constituting the shell of the present invention may be acopolymer of the foregoing ethylenically unsaturated monomer carrying anactive methylene group with other ethylenically unsaturated monomers.

Specific examples of such other monomers are acrylic acid or saltsthereof, alkyl acrylates (such as methyl acrylate, ethyl acrylate,n-butyl acrylate, n-hexyl acrylate, benzyl acrylate, 2-ethylhexylacrylate, n-dodecyl acrylate, t-butyl acrylate, phenyl acrylate and2-naphthyl acrylate), methacrylic acid or salts thereof, alkylmethacrylates (such as methyl methacrylate, ethyl methacrylate,2-hydroxyethyl methacrylate, benzyl methacrylate, 2-hydroxypropylmethacrylate, phenyl methacrylate, cresyl methacrylate, 4-chlorobenzylmethacrylate, ethylene glycol dimethacrylate, n-butyl methacrylate,n-hexyl methacrylate, 2-ethylhexyl methacrylate and n-dodecylmethacrylate), vinyl esters (such as vinyl acetate, vinyl benzoate andpivaloyloxy ethylene), acrylamides (such as acrylamide, methylacrylamide, ethyl acrylamide, propyl acrylamide, butyl acrylamide,t-butyl acrylamide, cyclohexyl acrylamide, benzyl acrylamide,hydroxymethyl acrylamide, methoxyethyl acrylamide, dimethylaminoethylacrylamide, phenyl acrylamide, dimethyl acrylamide, diethyl acrylamide,β-cyanoethyl acrylamide, diacetone acrylamide and2-acrylamido-2-methylpropanesulfonic acid), methacrylamides (such asmethacrylamide, methyl methacrylamide, ethyl methacrylamide, propylmethacrylamide, butyl methacrylamide, t-butyl methacrylamide, cyclohexylmethacrylamide, benzyl methacrylamide, hydroxymethyl methacrylamide,methoxyethyl methacrylamide, dimethylaminoethyl methacrylamide, phenylmethacrylamide, dimethyl methacrylamide, diethyl methacrylamide andβ-cyanoethyl methacrylamide), styrenes (such as styrene, methyl styrene,dimethylstyrene, trimethylstyrene, ethylstyrene, isopropylstyrene,chlorostyrene, methoxystyrene, acetoxystyrene, chlorostyrene,dichlorostyrene, bromostyrene and methyl vinylbenzoate), divinylbenzene,acrylonitrile, methacrylonitrile, N-vinylpyrrolidone,N-vinyloxazolidone, vinylidene chloride, phenyl vinyl ketone, itaconicacid, maleic acid, monoalkyl itaconates (such as monomethyl itaconateand monoethyl itaconate), monoalkyl maleates (such as monomethyl maleateand monoethyl maleate) and citraconic acid.

In the core/shell latex polymer of the present invention, the content ofthe monomer units carrying active methylene groups in the shell polymermay arbitrarily be changed depending on the desired characteristicproperties of the shell polymer and may be in the range of from 0.1 to100% by weight. In this respect, if the content thereof in the resultingcopolymer increases, the foregoing various effects are improved, butthese effects are sometimes saturated at a content of more than acertain level and preferably 0.1 to 60% by weight, in particular, 1 to40% by weight.

In the core/shell latex polymer of the present invention, the ratio ofthe amount of the core polymer to that of the shell polymer mayarbitrarily be changed, but the weight ratio: core/shell ranges from10/90 to 95/5, preferably 20/80 to 95/5 and particularly preferably30/70 to 90/10. If the rate of the core polymer is too low, the effectdue to the concentration of the active methylene monomer on the shellportion is reduced, while if the rate of the shell polymer is too low,it is difficult to form a distinct core/shell structure.

The particle size of the core/shell latex polymer is not more than 1.0μm, preferably not more than 0.7 μm, particularly preferably not morethan 0.5 μm and preferably not less than 0.00001 μm, like the particlesize of the core polymer particles defined above.

As has been well-known in the field of the core/shell latex-formingtechnique in the emulsion polymerization, the combination of a corepolymer and a shell polymer whose polarity is very close to one anotherand which are accordingly compatible with one another does not sometimesform a desired core/shell structure. However, the conjugated dienemonomer used in the core portion in the present invention has very lowpolarity and therefore, may form effective core/shell structurestogether with all of the foregoing monomers used in the shell portion.Morever, even if a monomer having polarity close to that of the corepolymer is used in the shell, a desired core/shell particles can beobtained by three-dimensionally crosslinking the core polymer using acrosslinking monomer.

In the core/shell latex polymer of the present invention, either or bothof the core and shell polymers may be crosslinked. The molecular weightof the polymer thus obtained is infinite. The molecular weight of theun-crosslinked polymer of the present invention varies depending on thekinds of monomers used and conditions for synthesizing the same, butranges from 5000 to 2,000,000. The molecular weight thereof can beadjusted through the use of a chain transfer agent depending onpurposes.

In addition, as has been known in the field of the radicalpolymerization technique, the shell polymer in the core/shell latexpolymer of the invention may form a graft polymer through partial graftpolymerization during the copolymerization of the conjugated dienemonomer. In this case, the resulting latex polymer comprises, as awhole, a mixture of three kinds of polymers, i.e., the core polymer, theforegoing graft polymer and un-grafted shell polymer.

Examples of preferred compounds used in the core/shell latex of thepresent invention will be listed below, but the present invention is notrestricted to these specific examples. The structures of each latexcompound given below are described in the order of the core polymerstructure (copolymerizable monomer and composition), the shell polymerstructure (copolymerizable monomer and composition) and the ratio:core/shell. The compositional ratio for copolymerization and thecore/shell ratio are expressed in terms of the ratio of weightpercentages.

P-1 to 12: core=styrene/butadiene (37/63)

P-1: shell=styrene/M-1 (98/2); core/shell=50/50

P-2: shell=styrene/M-1 (96/4); core/shell=50/50

P-3: shell=styrene/M-1 (92/8); core/shell=50/50

P-4: shell=styrene/M-1 (84/16); core/shell=50/50

P-5: shell=styrene/M-1 (68/32); core/shell=50/50

P-6: shell=styrene/M-1 (84/16); core/shell=67/33

P-7: shell=styrene/M-2 (84/16); core/shell=75/25

P-8: shell=n-butyl acrylate/M-1 (96/4); core/shell=50/50

P-9: shell=n-butyl acrylate/M-2 (92/8); core/shell=50/50

P-10: shell=n-butyl acrylate/M-1 (84/16); core/shell=50/50

P-11: shell=methyl acrylate/M-7 (84/16); core/shell=50/50

P-12: shell=styrene/methyl acrylate/M-3 (21/63/16); core/shell=50/50

P-13 to 16: core=styrene/butadiene (23/77)

P-13: shell=styrene/M-1 (92/8); core/shell=50/50

P-14: shell=styrene/M-2 (84/16); core/shell=50/50

P-15: shell=n-butyl acrylate/M-1 (84/16); core/shell=50/50

P-16: shell=n-butyl acrylate/M-8/acrylic acid (80/16/4);core/shell=50/50

P-17 to 22: core=polybutadiene (100)

P-17: shell=styrene/M-1 (84/16); core/shell=50/50

P-18: shell=ethyl acrylate/M-7/methacrylic acid (65/15/20)core/shell=85/15

P-19: shell=n-butyl acrylate/M-7 (84/16); core/shell=50/50

P-20: shell=n-butyl acrylate/M-2 (84/16); core/shell=50/50

P-21: shell=2-ethylhexyl acrylate/M-24 (84/16); core/shell=50/50

P-22: shell=n-butyl acrylate/M-18(84/16); core/shell=50/50

P-23 to 25: core=polyisoprene (100)

P-23: shell=styrene/acrylonitrile/M-1 (63/21/16); core/shell=90/10

P-24: shell=methyl methacrylate/ethyl acrylate/M-2/Na2-acrylamido-2-methylpropanesulfonate (15/65/15/5); core/shell=75/25

P-25: shell=styrene/M-1 (84/16); core/shell=20/80

P-26 to 28: core=styrene/butadiene (49/51)

P-26: shell=styrene/butyl acrylate/M-1 (25/60/15); core/shell=50/50

P-27: shell=M-1 (100); core/shell=90/10

P-28: shell=lauryl methacrylate/butyl acrylate/M-7 (30/55/15);core/shell=40/60

P-29: core=styrene/butadiene (63/37); shell=butylacrylate/2-hydroxyethyl methacrylate/M-2 (65/15/20); core/shell=50/50

P-30: core=acrylonitrile/butadiene (50/50); shell=butyl acrylate/2-butylmethacrylate/M-1 (40/40/20); core/shell=50/50

P-31: core=acrylonitrile/styrene/butadiene (25/25/50); shell=butylacrylate/M-1 (92/8); core/shell=50/50

P-32: core=ethyl acrylate/butadiene(40/60);shell=styrene/divinylbenzene/M-1 (79/5/16); core/shell=50/50

P-33: core=ethyl acrylate/styrene/butadiene(40/30/30); shell=ethylhexylacrylate/M-7 (84/16); core/shell=50/50

P-35: core=styrene/butadiene (37/63); shell=styrene/M-1 (84/16);core/shell=85/15

P-36, 37: core=styrene/butadiene (22/78)

P-36: shell=styrene/M-2 (84/16); core/shell=50/50

P-37: shell=n-butyl acrylate/M-8 (84/16); core/shell=50/50

P-38: core=polybutadiene (100); shell=ethyl acrylate/M-7/methacrylicacid (65/15/20); core/shell=75/25

P-39: core=ethyl acrylate/butadiene(50/50);shell=styrene/divinylbenzene/M-1 (79/5/16); core/shell=50/50

P-40 to 44: core=poly(n-dodecyl methacrylate) (100)

P-40: shell styrene/M-1 (92/8); core/shell 50/50

P-41: shell=styrene/M-1 (84/16); core/shell=50/50

P-42: shell=ethyl acrylate/M-1 (96/4); core/shell=50/50

P-43: shell=ethyl acrylate/M-1 (92/8); core/shell=50/50

P-44: shell=styrene/methyl acrylate/M-3 (21/63/16); core/shell=50/50

P-45: core=poly(n-butyl acrylate) (100); shell=styrene/M-2 (84/16);core/shell=50/50

P-46, 47: core=poly(ethylene glycol dimethacrylate/n-butyl acrylate)(10/90)

P-46: shell=styrene/M-1 (84/16); core/shell=50/50

P-47: shell=methyl acrylate/M-7/methacrylic acid (65/15/20);core/shell=75/25

P-48 to 51: core=poly(ethylene glycol dimethacrylate/n-butyl acrylate)(20/80)

P-48: shell=styrene/M-1 (84/16); core/shell=50/50

P-49: shell=styrene/M-1 (84/16); core/shell=75/25

P-50: shell=methyl acrylate/M-8/Na 2-acrylamido-2-methylpropanesulfonate(80/15/5); core/shell=75/25

P-51: shell=n-butyl acrylate/M-1 (84/16); core/shell=50/50

P-52 to 54: core=polyvinyl acetate (100)

P-52: shell=styrene/M-1 (84/16); core/shell=50/50

P-53: shell=styrene/divinylbenzene/M-24 (79/5/16); core/shell=50/50

P-54: shell=n-dodecyl methacrylate/butyl acrylate/M-7 (30/55/15);core/shell=40/60

P-55 to 57: core=poly(divinylbenzene/2-ethylhexyl acrylate) (10/90)

P-55: shell=methyl acrylate/M-1 (84/16); core/shell=50/50

P-56: shell=methyl acrylate/styrene/M-1 (74/10/16); core/shell=50/50

P-57: shell=M-1 (100); core/shell=90/10

P-58 to 60: core=poly(divinylbenzene/styrene/2-ethylhexyl acrylate)(10/23/67)

P-58: shell=methyl acrylate/M-1 (84/16); core/shell=50/50

P-59: shell=methyl acrylate/styrene/M-1 (74/10/16); core/shell=50/50

P-60: shell=ethyl acrylate/2-hydroxyethyl methacrylate/M-5 (65/15/20);core/shell=85/15

P-61: core=poly(ethylene glycol dimethacrylate/vinyl palmitate/n-butylacrylate) (20/20/60); shell=ethylene glycoldimethacrylate/styrene/n-butyl methacrylate/M-1 (5/40/40/15);core/shell=50/50

P-62: core=poly(trivinylcyclohexane/n-butyl acrylate/styrene)(10/55/35); shell=methyl acrylate/M-1/Na2-acrylamido-2-methylpropanesulfonate (88/7/5); core/shell=70/30

P-63, 64: core=poly(divinylbenzene/styrene/methyl methacrylate)(10/45/45)

P-63: shell=n-butyl acrylate/M-1 (84/16); core/shell=50/50

P-64: shell=n-dodecyl acrylate/ethyl acrylate/M-21 (60/30/10);core/shell=50/50

P-65, 66: core=poly(p-vinyltoluene/n-dodecyl methacrylate) (70/30)

P-65: shell=methyl acrylate/n-butyl methacrylate/M-2/acrylic acid(30/55/10/5); core/shell=50/50

P-66: shell=n-butyl acrylate/M-19 (84/16); core/shell=70/30

The core/shell latex polymer of the present invention can easily beprepared by emulsion-polymerizing a monomer for forming the shell,wherein the monomer is added, in one portion or dropwise, to a corelatex polymer in the form of a water dispersion obtained by emulsionpolymerization.

The emulsion polymerization can in general be carried out by emulsifyinga monomer in water or a mixed solvent of water and a water-miscibleorganic solvent (such as methanol, ethanol or acetone), preferably inthe presence of at least one emulsifying agent and then carrying outemulsion polymerization in the presence of a radical initiator at atemperature generally ranging from 30 to about 100° C., preferably 40 toabout 90° C. The amount of the water-miscible organic solvent rangesfrom 0 to 100% by volume, preferably 0 to 50% by volume based on theamount of water.

The polymerization reaction is in general carried out in the presence ofa radical polymerization initiator in an amount ranging from 0.05 to 5%by weight and optionally an emulsifying agent in an amount ranging from0.1 to 10% by weight, on the basis of the weight of the monomer to bepolymerized. The polymerization initiator may be azobis compounds,peroxides, hydroperoxides and redox solvents such as potassiumpersulfate, ammonium persulfate, t-butyl peroctoate, benzoyl peroxide,isopropyl carbonate, 2,4-dichlorobenzyl peroxide, methyl ethyl ketoneperoxide, cumene hydroperoxide, dicumyl peroxide,2,2'-azobisisobutyrate, 2,2'-azobis(2-amidinopropane)hydrochloride andcombination of potassium persulfate and sodium hydrogen sulfite.

The emulsifying agents usable herein may be anionic, cationic,amphoteric and nonionic surfactants as well as water-soluble polymers.Specific examples thereof are sodium laurate, sodium dodecylsulfate,sodium 1-octoxycarbonylmethyl-1-octoxycarbonylmethanesulfonate, sodiumlaurylnaphthalenesulfonate, sodium laurylbenzenesulfonate, sodiumlaurylphosphate, cetyltrimethylammonium chloride,dodecyltrimethyleneammonium chloride, N-2-ethylhexylpyridinium chloride,polyoxyethylene nonyl phenyl ether, polyoxyethylene sorbitan laurylester, sodium dodecyl diphenyl ether disulfonate, sodium2-tetradecene-1-sulfonate, sodium 3-hydroxytetradecane-1-sulfonate,gelatin, PVA, and emulsifying agents and water-soluble polymers asdisclosed in J.P. KOKOKU No. Sho 53-6190, with anionic or nonionicsurfactants and water-soluble polymers being preferred among others.

When carrying out the emulsion polymerization, the monomer is preferablydropwise added to the polymerization system in order to preventgeneration of heat during the polymerization and to form a more distinctcore/shell structure.

Moreover, when the monomer for the shell polymer is polymerized afterforming the core latex particles by the emulsion polymerization in thepresence of the foregoing initiator and emulsifying agent, thepolymerization of the monomer may be performed in the presence orabsence of an additional emulsifying agent. The supplementary additionof an emulsifying agent is often needed from the viewpoint of ensuringthe stability of the resulting latex polymer. On the contrary, thepresence of an excess emulsifying agent sometimes results in theformation of particles comprising only undesired shell polymers asby-products. Therefore, the amount of the emulsifying agentsupplementarily added after the formation of the core polymer is limitedto the range of from 0.001 to 2% by weight on the basis of the weight ofthe core particles or the polymerization is preferably carried out inthe absence of any supplementary emulsifying agent.

To form a latex having an effective core/shell structure, the coreparticles are preferably polymerized as complete as possible before theaddition of the monomer for forming the shell polymer. Morespecifically, the degree of polymerization thereof is not less than 90%,preferably not less than 95% and particularly preferably it issubstantially 100%.

The active methylene units serve as reactive groups in the improvementof the film strength of the latex polymer/gelatin composite film andvarious properties of paints and varnishes as well as adhesives. Forthis reason, the amount of the active methylene units present on thelatex surface becomes an important factor which affects the quality ofthe latex polymer. The core/shell latex of the present invention isbasically effective in that the active methylene units can beconcentrated on the latex surface serving as an important site.Moreover, the core/shell latex shows an effect of unexpectedly improvingthe film strength of, for instance, a gelatin film in a wet condition,which cannot be predicted only on the basis of the concentration of theactive methylene units present on the surface thereof. In addition,other required functions such as a film-forming ability and physicalproperties (for instance, control of brittleness) of the resulting filmor composite film with gelatin can be imparted to the core portionindependent of the shell portion by, for instance, controlling the Tgvalue of the entire latex.

The core/shell latex particles of the present invention can be obtainedby the emulsion polymerization discussed above in the form of a waterdispersion, but it is also possible to convert it into powder of fineparticles while maintaining the core/shell structure thereof.

Such powdery product can be obtained by any known methods such aslyophilization; aggregation-filtration using a strong acid or a salt; oraggregation-filtration through repetition of freezing-thawing of aliquid.

Then the silver halide photographic light-sensitive material as thesecond aspect of the present invention will hereinafter be explained inmore detail.

Gelatin is preferably used as a binder in the silver halide emulsionlayer of the present invention and other hydrophilic colloidal layers,but other hydrophilic colloids may be used in combination. Examples ofsuch hydrophilic colloids include various kinds of synthetic hydrophilicpolymer materials, for instance, gelatin derivatives, graft polymers ofgelatin and other polymers, proteins such as albumin and casein,cellulose derivatives such as hydroxyethyl cellulose, carboxymethylcellulose and cellulose sulfuric acid esters, sodium alginate, sugarderivatives such as starch derivatives, and homo- and copolymers such aspolyvinyl alcohol, polyvinyl alcohol partially modified with acetal,poly-N-vinylpyrrolidone, polyacrylic acid, polymethacrylic acid,polyacrylamide, polyvinyl imidazole and polyvinyl pyrazole.

Gelatin may be gelatin treated with lime and gelatin treated with anacid as well as gelatin hydrolyzates and enzyme-decomposed products ofgelatin.

Examples of silver halide photographic light-sensitive materialscontaining the latex of the present invention specifically include X-raysensitive light-sensitive materials, light-sensitive materials forprinting, those for monochromatic photographing, color negativelight-sensitive materials, color reversal light-sensitive materials andcolor printing paper.

In the light-sensitive materials for printing and X-ray sensitivelight-sensitive materials as preferred embodiments of the presentinvention, a sufficient effect can be expected irrespective of thecoated amount of gelatin as a binder, but the overall content of thewhole hydrophilic colloidal layers on the side of the silver halideemulsion layer is preferably not more than 3.0 g/m², particularlypreferably 1.0 to 2.5 g/m².

The core/shell. latex polymer of the invention is incorporated into atleast one of the silver halide emulsion layer, backing layer and otherhydrophilic colloid layers, in an amount ranging from 0.1 to 200% byweight, preferably 5 to 150% by weight on the basis of the amount ofgelatin present in the hydrophilic colloid layer.

The silver halide emulsion used for preparing the light-sensitivematerial of the present invention may comprise, as silver halidecomponents, any silver halide currently used in the silver halideemulsion such as silver bromide, silver iodobromide, silver chloride,silver chlorobromide and silver chloroiodobromide. The silver halidegrains may be those prepared by the acid method, neutral method orammonium method. The silver halide grain may be those in which silverhalides are uniformly distributed throughout each grain or a core/shellgrain whose surface layer has a silver halide composition differs fromthat of the inner portion thereof as well as those in which latentimages are mainly formed on the surface of the grain or mainly formed inthe inner portion. The silver halide grain usable in the invention mayhave any shape. An example of preferred shapes of the grain is a cubehaving {100} plane as the crystal surface. Alternatively, it is alsopossible to use, for instance, octahedron, dodecahedron andtetradecahedron which can be produced by the methods disclosed in, forinstance, U.S. Pat. Nos. 4,183,756 and 4,225,666, J.P. KOKAI No. Sho55-26589, J.P. KOKOKU No. Sho 55-42737 and J. Photogr. Sci., 21-39(1973). Moreover, those having twin crystal planes may likewise be usedin the invention. The silver halide grains used in the invention maycomprise those having uniform shape or a mixture of grains havingvarious shapes. In the present invention, a monodispersed emulsion ispreferred. With regard to monodispersed silver halide grains present inthe monodispersed emulsion, the rate (by weight) of silver halide grainswhose particle size falls within the range: γ (average particle size)±10% is preferably not less than 60% based on the total weight of thesilver halide grains.

Metal ions may be incorporated into the interior and/or the surface ofsilver halide grains used in the emulsion of the present invention byadding, thereto, cadmium salts, zinc salts, lead salts, thallium salts,iridium salts or complex salts thereof, rhodium salts or complex saltsthereof, or iron salts or complex salts thereof during processes forforming and/or growing the grains. In the preparation of thephotographic emulsion used in the invention, the sulfur-sensitization orgold-sulfur sensotization may be used or may be used in combination withthe reduction sensitization using a reducing substance or noble metalsensitization using a noble metal compound. As the light-sensitiveemulsion, the foregoing emulsions may be used alone or in combination.When practicing the present invention, various stabilizers such as4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene, 5-mercapto-1-phenytetrazoleand 2-mercaptobenzothiazole may be used after the foregoing chemicalsensitization. Moreover, a silver halide-solubilizing agent such asthioethers and/or a crystal habit-controlling agent such as mercaptogroup-containing compounds or sensitizing dyes may optionally be used.

In the silver halide photographic light-sensitive material of theinvention, the photographic emulsion may be spectrally sensitized with asensitizing dye so as to make the emulsion sensitive to blue light rayshaving relatively long wavelengths, green light rays, red light rays orinfrared light rays. Examples of such dyes to be used are cyanine dyes,merocyanine dyes, complex cyanine dyes, complex merocyanine dyes,holopolar cyanine dyes, hemicyanine dyes, styryl dyes and hemioxonoldyes. These sensitizing dyes may be used alone or in any combination.Combinations of sensitizing dyes are often used for the purpose ofsupersensitization. The silver halide photographic light-sensitivematerial of the invention may comprise, in its hydrophilic colloidlayer, water-soluble dyes as filter dyes, or for various other purposessuch as anti-irradiation and anti-halation. Examples of such dyes areoxonol dyes, hemioxonol dyes, styryl dyes, merocyanine dyes, cyaninedyes and azo dyes. Among these, oxonol dyes, hemioxonol dyes andmerocyanine dyes are useful. Specific examples of dyes usable in theinvention are those disclosed in German Patent No. 616,007, U.K. PatentNos. 584,609 and 1,117,429, J.P. KOKOKU Nos. Sho 26-7777, Sho 39-22069and Sho 54-38129, J.P. KOKAI Nos. Sho 48-85130, Sho 49-99620, Sho49-114420 and Sho 49-129537, PB Report No. 74175 and Photo. Abstr., 128('21). These dyes are suitably used, in particular, in the bright roomreversal light-sensitive material. It is also possible to use adispersion of dye solid fine particles as disclosed in Japanese PatentApplication Serial No. Hei 5-244717, pp. 23-30. If the silver halidephotographic light-sensitive material of the present invention comprisesa dye and/or a ultraviolet light absorber in its hydrophilic colloidallayer, they may be mordanted with, for instance, a cationic polymer.

The latex polymer of the present invention may likewise be used in colorsilver halide photographic light-sensitive materials.

The color photographic light-sensitive material comprises at least oneof blue-sensitive, green-sensitive and red-sensitive silver halideemulsion layers on a substrate and the number of the silver halideemulsion layer, the number of light-insensitive layer and the orderthereof may arbitrarily be selected. A typical example thereof is asilver halide photographic light-sensitive material which comprises asubstrate and at least one light-sensitive layer comprising a pluralityof silver halide emulsion layers which have substantially the same colorsensitivity, but differ in the degree of sensitivity and thelight-sensitive layer is a unit light-sensitive layer sensitive toeither of blue light rays, green light rays and red light rays. In themultilayered silver halide color photographic light-sensitive material,the unit light-sensitive layer has such an arrangement that thered-sensitive, green-sensitive and blue-sensitive layers are formed onthe substrate in this order from the side of the substrate.Alternatively, these layers may be arranged in the reverse order or maybe arranged such that light-sensitive layers having the same colorsensitivity sandwich a light-sensitive layer having different colorsensitivity. These layers may be successively applied or may be applied,at one time, in the form of a multiple layers (so-called simultaneousmultilayer-coating). These methods are currently used in this field andare not worth special mention.

A light-insensitive layer such as a variety of intermediate layers maybe formed between the foregoing silver halide light-sensitive layers oras the uppermost layer or the lowermost layer.

The intermediate layer may comprise couplers and/or DIR compounds asdisclosed in J.P. KOKAI Nos. Sho 61-43748, Sho 59-113438, Sho 59-113440,Sho 61-20037 and Sho 61-20038 and/or color-mixing inhibitors commonlyused in this field.

A plurality of silver halide emulsion layers constituting each unitlight-sensitive layer are disclosed in, for instance, German Patent No.1,121,470, U.K. Patent No. 923,045, J.P. KOKAI Nos. Sho 57-112751, Sho62-200350, Sho 62-206541, Sho 62-206543, Sho 56-25738, Sho 62-63936 andSho 59-202464 and J.P. KOKOKU Nos. Sho 55-34932 and Sho 49-15495.

The color light-sensitive material may comprises various kinds of colorcouplers and specific examples thereof are disclosed in patents listedin Research Disclosure (RD), No. 17643, VII-C˜G.

Yellow couplers preferably used in the invention are, for instance,those disclosed in U.S. Pat. Nos. 3,933,501, 4,022,620, 4,326,024,4,401,752 and 4,248,961, J.P. KOKOKU No. Sho 58-10739, U.K. Patent Nos.1,425,020 and 1,476,760, U.S. Pat. Nos. 3,973,968, 4,314,023, 4,511,649and 5,298,383, European Patent No. 249,473A and J.P. KOKAI No. Hei5-165171.

Magenta couplers are preferably 5-pyrazolone type and pyrazoloazole typecompounds, in particular, those disclosed in, for instance, U.S. Pat.Nos. 4,310,619 and 4,351,897, European Patent No. 73,636, U.S. Pat. Nos.3,061,432 and 3,725,067, Research Disclosure No. 24220 (June, 1984),J.P. KOKAI No. Sho 60-33552, Research Disclosure No. 24230 (June, 1984),J.P. KOKAI Nos. Sho 60-43659, Sho 61-72238, Sho 60-35730, Sho 55-118034and Sho 60-185951, U.S. Pat. Nos. 4,500,630, 4,540,654 and 4,556,630 andWO(PCT) No. 88/04795.

Cyan couplers are, for instance, phenolic and naphtholic couplers andpreferably those disclosed in for instance, U.S. Pat. Nos. 4,052,212,4,146,396, 4,228,233, 4,296,200, 2,369,929, 2,801,171, 2,772,162,2,895,826, 3,772,002, 3,758,308, 4,334,011 and 4,327,173, DEOS No.3,329,729, European Patent Nos. 121,365A and 249,453A, U.S. Pat. Nos.3,446,622, 4,333,999, 4,753,871, 4,451,559, 4,427,767, 4,690,889,4,254,212 and 4,296,199 and J.P. KOKAI Nos. Sho 61-42658 and Hei5-341467.

Colored couplers for correcting unnecessary absorption of color-formingdyes are preferably those disclosed in Research Disclosure No. 17643,III-G, U.S. Pat. Nos. 4,163,670, 5,266,456, 4,004,929 and 4,138,258,J.P. KOKOKU No. Sho 57-39413 and U.K. Patent No. 1,146,368.

Couplers whose color-forming dyes show appropriate diffusibility arepreferably those disclosed in U.S. Pat. No. 4,366,237, U.K. Patent No.2,125,570, European Patent No. 96,570, DEOS No. 3,234,533.

Typical examples of polymerized dye-forming couplers are disclosed in,for instance, U.S. Pat. Nos. 3,451,820, 4,080,211, 4,367,282, 4,409,320and 4,576,910 and U.K. Patent No. 2,102,137.

Couplers which release photographically useful residues along withcoupling can likewise preferably be used in the present invention. DIRcouplers which release development inhibitors are preferably thosedisclosed in the patents listed in the foregoing RD 17643, VII-F such asJ.P. KOKAI Nos. Sho 57-151944, Sho 57-154234, Sho 60-184248, Sho63-37346 and Hei 5-113635 and U.S. Pat. No. 4,248,962.

Couplers which release nucleating agents or development accelerators inthe form of images during development are preferably those disclosed inU.K. Patent Nos. 2,097,140 and 2,131,188 and J.P. KOKAI Nos. Sho59-157638 and sho 59-170840.

In addition, examples of other couplers usable in the light-sensitivematerials of the present invention include competing couplers disclosedin, for instance, U.S. Pat. No. 4,130,427; multi-equivalent couplersdisclosed in, for instance, U.S. Pat. Nos. 4,283,472, 4,338,393 and4,310,618; DIR redox compound-releasing couplers, DIR coupler-releasingcouplers, DIR coupler-releasing redox compounds or DIR redox-releasingredox compounds disclosed in, for instance, J.P. KOKAI Nos. Sho60-185950 and Sho 62-24252; couplers releasing dyes which causerecoloring after elimination disclosed in European Patent No. 173,302A;bleach accelerator-releasing couplers disclosed in, for instance, RDNos. 11449 and 24241 and J.P. KOKAI No. Sho 61-201247; ligand-releasingcouplers disclosed in, for instance, U.S. Pat. No. 4,553,477; and leucodye-releasing couplers disclosed in J.P. KOKAI No. Sho 63-75747.

These couplers used in the invention may be incorporated into thelight-sensitive material by various known dispersion method. Examples ofhigh boiling point solvents used in the oil-in-water dispersion methodsare those disclosed in, for instance, U.S. Pat. No. 2,322,027. Specificexamples of high boiling point organic solvents whose boiling points arenot less than 175° C. used in the oil-in-water dispersion methods arephthalic acid esters, esters of phosphoric acid or phosphonic acid,benzoic acid esters, amides, alcohols or phenols, aliphatic carboxylicacid esters, aniline derivatives and hydrocarbons. Moreover, auxiliarysolvents usable herein are, for instance, organic solvents having aboiling point of not less than about 30° C. and preferably not less than50° C. and not more than about 160° C. and typical examples thereof areethyl acetate, butyl acetate, ethyl propionate, methyl ethyl ketone,cyclohexanone, 2-ethoxyethyl acetate and dimethylformamide.

Specific examples of the processes in latex-dispersing methods, effectsthereof and latexes for impregnation are disclosed in, for instance,U.S. Pat. No. 4,199,363 and OLS Nos. 2,541,274 and 2,541,230.

Preferably, the color light-sensitive material has a overall filmthickness of the whole hydrophilic colloid layers on the side of theemylsion layer of not more than 28 μm and a film-swelling rate T_(1/2)of not more than 30 seconds. The film thickness herein means thatdetermined at 25° C. and relative humidity of 55% (maintained for 2days) and the film-swelling rate T_(1/2) can be determined according tothe method known in this art. For instance, it can be determined using aswellometer such as that disclosed in A. Green et al., Photogr. Sci.Eng., Vol. 19, No. 2, pp. 124-129. Moreover, 90% of the maximum swollenfilm thickness observed when the light-sensitive material is treatedwith a color developer at 30° C. for 3 minutes and 15 seconds is assumedto be the film thickness at saturation and T_(1/2) is defined to be atime required for reaching the thickness T_(1/2).

The film-swelling rate T_(1/2) can be adjusted by adding afilm-hardening agent to gelatin as a binder or by changing the elapsedtime conditions after the application thereof. Moreover, the swellingrate preferably ranges from 150 to 400%. The swelling rate herein can becalculated from the maximum swelling film thickness observed under theaforementioned conditions according to the equation: (maximum swellingfilm thickness-film thickness)/(film thickness).

In the present invention, antistatic agents are preferably used. Theantistatic agent is not restricted to specific ones and examples thereofinclude anionic polyelectrolytes such as polymers carrying carboxylicacid and carboxylate residues and/or sulfonic acid residues as disclosedin J.P. KOKAI Nos. Sho 48-22017, Sho 51-30725, Sho 51-129216 and Sho55-95942 and J.P. KOKOKU No. Sho 46-24159; cationic polymers such asthose disclosed in, for instance, J.P. KOKAI Nos. Sho 49-121523 and Sho48-91165 and J.P. KOKOKU No. Sho 49-24582; ionic surfactants (anionicand cationic) such as compounds disclosed in, for instance, J.P. KOKAINos. Sho 49-85826, Sho 49-33630, Sho 48-87826 and Sho 55-70837 and J.P.KOKOKU Nos. Sho 49-11567 and Sho 49-11568.

Most preferred antistatic agents are at least one crystalline metaloxide selected from the group consisting of ZnO, TiO₂, SnO₂, Al₂ O₃, In₂O₃, SiO₂, MgO, BaO, MoO₃ and V₂ O₅ ; or fine particles of double oxidesthereof (with, for instance, Sb, P, B, In, S, Si and/or C); or furthersol-like metal oxides or fine particles of double oxides thereof.

The conductive crystalline oxides or fine particles or needle-likefillers of double oxides thereof used in the invention have a volumeresistivity of not more than 10⁷ Ω-cm, more preferably not more than 10⁵Ω-cm. The particle size thereof desirably ranges from 0.001 to 1.0 μm,in particular, 0.001 to 0.3 μm. To more effectively impart conductivityto the antistatic layer, it is preferred to partially coagulate primaryfine particles of the conductive crystalline oxides or fine particles orfillers of double oxides thereof to a particle size ranging from 0.01 to0.2 μm prior to practical use.

Moreover, with regard to the conductivity achieved by the formation ofthe antistatic layer using these materials, the electrical resistancethereof in the raw state and after processing is preferably not morethan 10¹² Ω, more preferably not more than 10¹⁰ Ω and, in particular,not more than 10⁹.5 Ω.

In such case, the content of the antistatic agent in the light-sensitivematerial preferably ranges from 5 to 500 mg/m² and particularlypreferably 10 to 350 mg/m².

In addition, the amount of the binder preferably ranges from 1 to 500mg/m², in particular, 5 to 300 mg/m². The ratio of the amount of theconductive crystalline oxides or fine particles or needle-like fillersof double oxides thereof to that of the binder preferably ranges from1/300 to 100/1, more preferably 1/100 to 100/5.

The light-sensitive material of the present invention preferably hasslipping properties. The slipping properties may be imparted to eitherthe surface of the light-sensitive layer or the backing layer, buthigher effect can be expected when imparting the properties to thebacking layer. The slipping properties are preferably not more than 0.25and not less than 0.01 as expressed in terms of the coefficient ofdynamic friction. In this respect, the measured value represents thatobserved when the surface is moved at a rate of 60 cm/m² with respect tostainless steel spheres having a diameter of 5 mm. In this evaluation, avalue of almost the same level is observed when using the surface of alight-sensitive layer as the counterpart material.

The slipping agents usable in the invention are, for instance,polyorganosiloxane as disclosed in J.P. KOKOKU No. Sho 53-292; higherfatty acid amides as disclosed in U.S. Pat. No. 4,275,146; higher fattyacid esters (esters of fatty acids having 10 to 24 carbon atoms withalcohols having 10 to 24 carbon atoms) as disclosed in J.P. KOKOKU No.Sho 58-33541, U.K. Patent No. 927,446 or J.P. KOKAI Nos. Sho 55-126238and Sho 58-90633; metal salts of higher fatty acids as disclosed in U.S.Pat. No. 3,933,516; esters of linear higher fatty acids with linearhigher alcohols as disclosed in J.P. KOKAI No. Sho 58-50534; andbranched alkyl group containing higher fatty acid-higher alcohol estersas disclosed in International Publication No. 90108115.8.

Moreover, higher fatty acids and derivatives thereof and higher alcoholsand derivatives thereof usable herein are, for instance, higher fattyacids and metal salts thereof; higher fatty acid esters; higher fattyacid amides; esters of higher fatty acids with polyhydric alcohols;higher aliphatic alcohols; monoalkylphosphites, dialkylphosphites,trialkylphosphites, monoalkylphosphates, dialkylphosphates andtrialkylphosphates of higher aliphatic alcohols; and higher aliphaticalkylsulfonic acids and amide compounds and salts thereof.

In addition, preferably used further include, for instance, higher fattyacid-higher alcohol esters disclosed in, for instance, Japanese PatentApplication Serial Nos. Hei 5-153909, Hei 5-153910 and Hei 5-345871.

Moreover, the slipping agents used in the invention may be dispersed inorganic solvents by various methods. Examples of methods for dispersingthe same in organic solvents include a method comprising dispersing aslipping agent in an organic solvent in the solid state using a ballmill or sand grinder; a method comprising dissolving a slipping agent inan organic solvent with heating and precipitating by cooling withstirring to disperse the agent in the organic solvent; a methodcomprising dissolving a slipping agent in an organic solvent withheating, adding the solution to an organic solvent maintained atordinary temperature or cooled and cooling the mixture to separate outthe agent and to thus disperse it in the organic solvent; or a methodcomprising emulsifying a slipping agent using two organic solventsincompatible with one another. Examples of dispersing devices may be anycurrently used one, in particular, ultrasonic dispersing devices andhomogenizers.

The substrate for the light-sensitive material of the invention may be,for instance, those made from cellulose triacetate, cellulose diacetate,nitrocellulose, polystyrene, polyethylene terephthalate, baryta paperand polyethylene-coated paper.

These substrates may be subjected to a corona discharge treatment or mayoptionally be subjected to an undercoating treatment by any knownmethod.

The present invention may likewise be applied to silver halidephotographic light-sensitive materials comprising transparent magneticrecording layers. The conventional silver halide photographiclight-sensitive material (hereinafter simply referred to as"light-sensitive material") simply provides image information duringphotographing and printing, but the application of a transparentmagnetic recording layer to the whole surface of the light-sensitivelayer, as disclosed in J.P. KOKAI Nos. Hei 4-68336 and Hei 4-73737,permits the input, to the material, of various information such as thephotographing date and time, the weather, conditions for photographingsuch as reduction/expansion ratio, the reprint number, portions to bezoomed in, messages and conditions for development and printing inaddition to images. Moreover, the foregoing information may likewise beinputted to image-reproducing apparatuses such as television and videotape recorder through the use of such magnetic recording layer. In thisrespect, it is desired to eliminate any effect of dust due toelectrification, to improve the slipping properties of films and toeliminate any influence of curl of the film (including that of thesubstrate).

The transparent magnetic recording layer will further be detailed below.

Examples of magnetic particles usable in the present invention includeferromagnetic iron oxides (FeOx, 4/3<×≦3/2) such as γ-Fe₂ O₃ ; Co-coatedferromagnetic iron oxides (FeOx, 4/3<×≦3/2) such as Co-coated γ-Fe₂ O₃ ;Co-coated magnetite; other Co-containing ferromagnetic iron oxides;Co-containing magnetite; ferromagnetic chromium dioxide; ferromagneticmetals; ferromagnetic alloys; other ferrites such as hexagonalBa-ferrite, Sr-ferrite, Pb-ferrite and Ca-ferrite; or solid solutions orion-substituted bodies thereof, with Co-coated ferromagnetic iron oxidessuch as Co-coated γ-Fe₂ O₃ whose Fe²⁺ /Fe³⁺ ratio ranges from 0 to 10%being preferred because of their high permeability.

The shape of the ferromagnetic material may be needle-like, ricegrain-like, spherical, cube-like and plate-like ones, but needle-likeshape is preferred because of its high electromagnetic conversioncharacteristics. The needle-like ferromagnetic material preferably has aparticle size ranging from 0.01 to 0.8 μm, more preferably 0.05 to 0.3μm for the major axis and a major axis/minor axis ranging from 2 to 100and more preferably 4 to 15. The specific surface area thereof ispreferably not less than 20 m² /g, in particular, not less than 30 m² /gas expressed in terms of S_(BET).

The saturation magnetization (σs) of the ferromagnetic material ispreferably as high as possible, but preferably not less than 50 emu/g,more preferably not less than 70 emu/g and practically not more than 100emu/g. In addition, the rectangularity ratio (σr/σs) of theferromagnetic material is preferably not less than 40%, more preferablynot less than 45%. If the coercive force (Hc) is too low, it is liableto be erased, while if it is too high, it is impossible to writedepending on systems and therefore, the material should have a properrectangularity ratio. It is thus not less than 200 Oe not more than 2000Oe and more preferably not less than 650 Oe and not more than 950 Oe.

These ferromagnetic particles may be surface-treated with silica and/oralumina such as those disclosed in, for instance, J.P. KOKAI Nos. Sho59-23505 and Hei 4-096052. Moreover, they may be surface-treated withinorganic and/or organic materials such as those disclosed in J.P. KOKAINos. Hei 4-195726, Hei 4-192116, Hei 4-259911 and Hei 5-081652. Furtherthe surface of these ferromagnetic particles may be treated with asilane coupling agent or a titanium coupling agent.

The binder usable in the invention may be known thermoplastic resins,thermosetting resins, radiation-curable resins, reactive resins, acid-,alkali- or biodegradable polymers, naturally occurring polymers (such ascellulose derivatives and sugar derivatives) and mixture thereof, whichhave been used as binders for magnetic recording media. The foregoingresins preferably has a Tg value ranging from -40° C. to 300° C., aweight-average molecular weight ranging from 2000 to 1,000,000,preferably 5000 to 300,000.

Among these binders, preferred are cellulose di(or tri)acetate.

These binders may be used alone or in combination and may be hardened byaddition of an epoxy, aziridine or isocyanate type known crosslinkingagent and/or a radiation-curable vinyl monomer. Particularly preferredare isocyanate type crosslinking agents and examples thereof aretolylene diisocyanate, hexamethylene diisocyanate, xylylenediisocyanate, reaction products of these isocyanates with polyols (suchas reaction product of 3 mole of tolylene diisocyanate with one mole oftrimethylolpropane) and polyisocyanates prepared by condensing theseisocyanates.

In addition, examples of crosslinking agents carrying epoxy groups arepreferably trimethylolpropane, triglycidyl adducts and tetraglycidyladducts of pentaerythritol. The radiation-curable vinyl monomers arecompounds capable of being polymerized through irradiation with radiantrays and preferred examples thereof are (meth)acrylates of polyethyleneglycol having two (meth)acryloyl groups such as diethylene glycoldi(meth)acrylate and triethylene glycol di(meth)acrylate;trimethylolpropane tri(meth)acrylate; pentaerythritoltetra(meth)acrylate; dipentaerythritol penta(meth)acrylate;dipentaerythritol hexa(meth)acrylate; and reaction products ofpolyisocyanates with hydroxy(meth)acrylate compounds.

The amount of these crosslinking agents preferably ranges from 5 to 45%by weight based on the total amount of binder including the crosslinkingagent.

The magnetic recording layer of the present invention may also comprisea hydrophilic binder such as water-soluble polymers, cellulose esters,latex polymers and water-soluble polyesters. Specific examples ofwater-soluble polymers include gelatin, gelatin derivatives, casein,agar, sodium alginate, starch, polyvinyl alcohol, acrylic acid copolymerand maleic anhydride copolymer, specific examples of cellulose estersare carboxymethyl cellulose and hydroxyethyl cellulose. Specificexamples of latex polymers are vinyl chloride moiety-containingcopolymers, vinylidene chloride moiety-containing copolymers, acrylatemoiety-containing copolymers, vinyl acetate moiety-containing copolymersand butadiene moiety-containing copolymers. Among these, most preferredis gelatin.

The film-hardening agent for gelatin is, for instance,2-hydroxy-4,6-dichloro-1,3,5-triazine, divinylsulfone, isocyanatesdisclosed in, for instance, U.S. Pat. No. 3,103,437, azilidine compoundsdisclosed in, for instance, U.S. Pat. Nos. 3,017,280 and 2,983,611, andcarboxyl group-active type film-hardening agents disclosed in, forinstance, U.S. Pat. No. 3,321,313. The amount of the film-hardeningagent used in general ranges from 0.01 to 30% by weight, preferably 0.05to 20% by weight based on the weight of the dry gelatin.

The foregoing magnetic material may be dispersed in the binder byvarious known means, preferably a kneader, a pin type mill and anannular type mill as well as a combination of a kneader and a pin typemill and a combination of a kneader and an annular type mill.

The thickness of the magnetic recording layer ranges from 0.1 to 10μ,preferably 0.2 to 5μ and more preferably 0.3 to 3μ.

The weight ratio of the magnetic particles to the binder preferablyranges from 0.5:100 to 60:100 and more preferably 1: 100 to 30:100.

The coated amount of the magnetic material ranges from 0.005 to 3 g/m²,preferably 0.01 to 2 g/m² and more preferably 0.02 to 0.5 g/m².

The magnetic recording layer of the invention can be applied onto theback face of a substrate for photographs by coating or printingthroughout the whole surface or in a striped pattern. The magneticrecording layer may be applied thereto by, for instance, air doctorcoating, blade coating, air knife coating, squeeze coating, coatingthrough impregnation, reverse roll coating, transfer roll coating,gravure coating, kiss-roll coating, cast coating, spray coating, dipcoating, bar coating and extrusion coating as well as other methods.These methods are specifically described in "Coating Engineering", pp.253-277, published by Asakura Shoten (Showa 46 (1971), March 20).

Various functions such as lubrication-improving properties,curl-controlling properties, antistatic properties, adhesion-inhibitoryproperties and head-polishing properties may be imparted to the magneticrecording layer or these functions may be imparted to the layer byapplying a separate functional layer. A protective layer may, ifnecessary, be formed adjacent to the magnetic recording layer to improvethe resistance to scratches thereto and it is preferred to add, to theprotective layer, inorganic or organic fine particles (such as silica,SiO₂, SnO₂, Al₂ O₃, TiO₂, crosslinked polymethyl methacrylate, bariumcarbonate and silicone fine particles).

Then a polyethylenearomatic dicarboxylate type polyester substrate willbe detailed below, which is a substrate preferably used in the presentinvention.

The polyester is prepared using a diol and an aromatic dicarboxylic acidas essential components, but other dicarboxylic acids may be used incombination with the aromatic dicarboxylic acid. Examples of dibasicacids usable herein are terephthalic acid, isophthalic acid, phthalicacid, phthalic anhydride, naphthalene dicarboxylic acids (2,6-, 1,5-,1,4- and 2,7-), diphenylene p,p'-dicarboxylic acid, tetrachlorophthalicanhydride, succinic acid, glutaric acid, adipic acid, sebacic acid,succinic anhydride, maleic acid, fumaric acid, maleic anhydride,itaconic acid, citraconic anhydride, tetrahydrophthalic anhydride,3,6-endomethylenetetrahydrophthalic anhydride, 1,4-cyclohexanedicarboxylic acid, halogenated terephthalic acid,bis(p-carboxyphenol)ether, 1,1-dicarboxy-2-phenylethylene,1,4-dicarboxymethylphenol, 1,3-dicarboxy-5-phenylphenol and sodium3-sulfoisophthalate. The aromatic dicarboxylic acid as an essentialcomponent may be the foregoing dicarboxylic acids each of which has atleast one benzene nucleus.

Specific examples of diols include ethylene glycol, 1,3-propanediol,1,2-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,1,7-heptanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol,1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanediol,1,1-cyclohexanedimethanol, catechol, resorcin, hydroquinone,1,4-benzenedimethanol, dimethylolnaphthalene, p-hydroxyethyloxybenzene(PHBA) and bisphenol A.

Moreover, mono-functional or tri-functional or higher hydroxylgroup-containing compounds or acid-containing compounds may becopolymerized. Moreover, in the polyester used in the invention,compounds each simultaneously carrying a hydroxyl and carboxyl groups(or esters thereof) in the molecule, such as salicylic acid, may becopolymerized.

Examples of the polymers thus formed are homopolymers such aspolyethylene terephthalate, polyethylene naphthalate and polycyclohexanedimethanol terephthalate (PCT); and copolymers of terephthalic acid,naphthalenedicarboxylic acid and ethylene glycol (molar ratio ofterephthalic acid to naphthalenedicarboxylic acid is preferably between0.9:0.1 and 0.1:0.9 and more preferably between 0.8:0.2 and 0.2:0.8.Particularly preferred are polyesters comprising2,6-naphthalenedicarboxylic acid moieties and more specifically,polyesters comprising 0.1 to 1.0 of 2,6-naphthalenedicarboxylic acid,with polyethylene 2,6-naphthalate being particularly preferred.

These homopolymers and copolymers can be synthesized by theconventionally known methods for preparing polyesters. For instance,they can be prepared in the light of the disclosure of "KOBUNSHIJIKKENGAKU (Experimental Methods for Polymers)", Vol. 5 "JUSHUKUGO ToJUFUKA (Polycondensation and Polyaddition)", pp. 103-136, KyoritsuPublishing Company (1980); and "GOSEI KOBUNSHI (Synthetic Polymers) V",pp. 187-286, Asakura Shoten (1971).

These polyesters preferably have an average molecular weight rangingfrom about 5000 to 200000.

Moreover, it is also possible to blend these polyesters with a minoramount of different kinds of polyesters, to incorporate moieties derivedfrom monomers constituting other polyesters into these polyestersthrough copolymerization, to incorporate monomers having unsaturatedbonds into these polyesters through copolymerization or to subject thesepolyesters to radical crosslinking, for the purpose of improving theadhesion thereof to the different polyesters.

Polymer blends of at least two polymers thus obtained can easily beformed by the methods disclosed in J.P. KOKAI Nos. Sho 49-5482, Sho64-4325 and Hei 3-192718, and Research Disclosure Nos. 283,739-41,284,779-82 and 294,807-14.

The polyesters used in the invention each has a Tg value of not lessthan 50° C., but they are not always handled under strictly controlledconditions. They are often exposed to a temperature of up to 40° C., inparticular, in the open air during midsummer and therefore, the Tg valuethereof used in the invention is preferably not less than 55° C. forsafety's sake. More preferably, the Tg value is not less than 60° C. andparticularly preferably not less than 70° C. Moreover, it is preferablynot less than 90° C. to aim at perfect. Moreover, the effect ofeliminating curl due to the thermal treatment is disappeared if thepolyester is exposed to a temperature of higher than the glasstransition temperature thereof. For this reason, the polyesterpreferably has a Tg value of not less than the temperature duringmidsummer, i.e., 40° C. which is a severe condition encountered when thepolyester is generally employed by the users.

Specific compounds of preferred polyesters usable in the invention willbe listed below, but the present invention is not restricted to thesespecific examples.

Examples of Polyester Compounds

BP-0: terephthalic acid (TPA)/ethylene glycol (EG) (100/100) (PET);Tg=80° C.

BP-1: 2,6-naphthalene dicarboxylic acid (NDCA)/ethylene glycol (EG)(100/100) (PEN); Tg=119° C.

BP-2: terephthalic acid (TPA)/cyclohexanedimethanol (CHDM) (100/100);Tg=93° C.

BP-3: TPA/bisphenol A (BPA) (100/100); Tg=192° C.

BP-4: 2,6--NDCA/TPA/EG (50/50/100); Tg=92° C.

BP-5: 2,6--NDCA/TPA/EG (75/25/100); Tg=102° C.

BP-6: 2,6--NDCA/TPA/EG/BPA (50/50/75/25); Tg=112° C.

BP-7: TPA/EG/BPA (100/50/50); Tg=105° C.

BP-8: TPA/EG/BPA (100/25/75); Tg=135° C.

BP-9: TPA/EG/CHDM/BPA (100/25/25/50); Tg=115° C.

BP-10: isophthalic acid (IPA)/NDCA/TPA/EG (20/50/30/100); Tg=95° C.

BP-11: NDCA/neopentyl glycol(NPG)/EG (100/70/30); Tg=105° C.

BP-12: TPA/EG/bisphenol (BP) (100/20/80); Tg=115° C.

BP-13: PHBA/EG/TPA (200/100/100); Tg=125° C.

BP-14: PEN/PET (60/40); Tg=95° C.

BP-15: PEN/PET (80/20); Tg=104° C.

BP-16: polyacrylate (PAr)/PEN (50/50); Tg=142° C.

BP-17: PAr/polycyclohexanedimethanol terephthalate (PCT) (50/50);Tg=118° C.

BP-18: PAr/PET (60/40); Tg=101° C.

BP-19: PEN/PET/PAr (50/25/25); Tg=108° C.

BP-20: TPA/5-sulfoisophthalic acid (SIP)/EG (95/5/100);

Tg=65° C.

BP-21: PEN/SIP/EG (99/1/100); Tg=115° C.

These substrates used in the invention each has a thickness of not lessthan 50 μm and not more than 300 μm. If it is less than 50 μm, thesubstrate cannot withstand the contraction stress generated in thelight-sensitive layer during drying. On the other hand, if it exceeds300 μm, this is contradict to the desired purpose of reducing thethickness for making the light-sensitive material compact. Morepreferably, it is preferably thick because of its firmness and thus thethickness ranges from 50 to 200 μm, more preferably 80 to 115 μm andparticularly preferably 85 to 105 μm.

The polyester substrate used in the invention is then heat-treatmentwhich should be carried out at a temperature of not less than 40° C. andnot more than the glass transition temperature for 0.1 to 1500 hours andthis treatment permits the formation of a film which seldom causescurling. More preferably, the heat-treatment is carried out at atemperature of not less than Tg-20° C. and less than Tg. Theheat-treatment may be performed at a constant temperature falling withinthe range defined above or may be carried out while cooling thesubstrate. In this respect, the average cooling speed preferably rangesfrom -0.01 to -20° C./hr and more preferably -0.1 to -5° C./hr.

The time for the heat-treatment is not less than 0.1 hour and not morethan 1500 hours, more preferably not less than 0.5 hr and not more than200 hours. This is because if it is less than 0.1 hour, a sufficienteffect cannot be expected, while if it exceeds 1500 hours, any furthereffect cannot be expected and the substrate may be liable to causecoloration and to become brittle.

To further improve the effect of eliminating the curling tendency, it ispreferred that the substrate be heat-treated at a temperature of notless than Tg and less than the melting point thereof (the fusiontemperature as determined by DSC) prior to the foregoing heat-treatmentto thus eliminate the heat history of the substrate and thereafter thesubstrate is again heat-treated at a temperature of not less than 40° C.and less than Tg as discussed above.

Such a heat-treatment may be applied to a substrate in a roll-like shapeor may be carried out while conveying web-like substrate. When asubstrate in a roll-like shape is heat-treated, the substrate at roomtemperature is directly transferred to a thermostatic chamber to subjectit to the heat-treatment or a web-like substrate is heated to a desiredtemperature during conveying the same, then wound up in a roll andfinally heat-treated. In the heat-treatment of a roll-like substrate,the substrate suffers from various superficial defects due toheat-contraction stress generated during the heat-treatment such asformation of wrinkles due to firm winding and the impression by the cutend at the core portion. Therefore, some consideration is needed toeliminate these drawbacks. For instance, the surface of the substrate ismade uneven (for instance, by coating the surface with conductiveinorganic fine particles such as SnO₂ /Sb₂ O₅ or colloidal silica) toreduce or relieve the squeak and to thus prevent the formation ofwrinkles due to firm winding or the thickness of the edge of thesubstrate is increased by fitting a knurling tool to the edge of thesubstrate to thus prevent the formation of any impression by the cut endat the core portion. The heat-treatment of the substrate in the form ofa web requires very long post-heat-treating process, but this method canprovides a substrate having excellent surface quality as compared withthat obtained after the heat-treatment of the substrate in the roll-likeshape.

These heat-treatments may be carried out at any stage, for instance,after the formation of substrate film, after a glow discharge treatmentof the substrate, after the application of a backing layer (ofantistatic agents, slipping agents or the like) or the application of anundercoating layer thereto. The heat-treatment is preferably carried outafter the application of an antistatic agent. This permits theelimination of any adhesion of dust due to electrification during theheat-treatment which results in the formation of superficial defects.

Various additives are preferably added to the polyester serving as asubstrate for photograph for further improvement of the functions of thesubstrate.

An ultraviolet light absorber may be incorporated into these polyesterfilms to impart a fluorescence-inhibitory effect and storage stabilityto the films. The ultraviolet light absorber is preferably those whichdo not have any absorption band within the visible light range and theamount thereof to be added usually ranges from 0.01 to 20% by weight,preferably about 0.05 to 10% by weight based on the weight of thepolyester film. Examples of ultraviolet light absorbers are benzophenoneultraviolet light absorbers such as 2,4-dihydroxybenzophenone,2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone,4-dodecyloxy-2-hydroxybenzophen one, 2,2',4,4'-tetrahydroxybenzophenoneand 2,2'-dihydroxy-4,4'-dimethoxybenzophenone; benzotriazole ultravioletlight absorbers such as 2-(2'-hydroxy-5-methylphenyl)benzotriazole,2-(2'-hydroxy-3',5'-di-t-butylphenyl)benzotriazole and2-(2'-hydroxy-3'-di-t-butyl-5'-methylphenyl)benzotriazole; and salicylicacid ultraviolet light absorbers such as phenyl salicylate and methylsalicylate.

Moreover, it is preferred to add inert inorganic particles and dyes tothe substrate in order to eliminate any light-piping phenomenon. The dyeused is not restricted to any specific one and the intended purpose canbe achieved by admixing, with the substrate, commercially available dyesfor polyesters such as Diaresin available from Mitsubishi ChemicalIndustries Ltd. and Kayaset available from Nippon Kayaku Co., Ltd. Thestaining density must be at least 0.01 expressed in terms of the colordensity in the visible light range as determined by a color densitometeravailable from Macbeth Company and more preferably it is not less than0.03.

An ability of easy slipping may be imparted to the polyester film usedin the invention depending on applications thereof and this can beperformed by addition of inert inorganic particles such as SiO₂, TiO₂,BaSO₄, CaCO₃, talc and kaolin.

When these polyester films are used as substrates, they are preferablysubjected to various surface-treatment to firmly adhere, to thesubstrates, photographic layer of a protective colloid mainly comprisinggelatin (such as light-sensitive silver halide emulsion layer,intermediate layer and filter layer) since all of these polyestersubstrates have hydrophobic surfaces. Examples of suchsurface-treatments are surface activation treatments such as treatmentswith chemicals, mechanical treatments, corona discharge treatments,flame treatments, ultraviolet light-irradiation, radiofrequencytreatments, glow discharge treatments, treatments with active plasma,laser treatments, treatments with mixed acid and ozone-oxidationtreatments. After such a surface-treatment, an undercoating layer may beapplied or a photographic emulsion layer may directly be applied to thepolyester substrate.

Among these surface-treatments, preferred are ultravioletlight-irradiation, flame treatments, corona discharge treatments andglow discharge treatments.

First of all, the ultraviolet light-irradiation treatments will bedetailed below. These treatments are preferably carried out using themethods as disclosed in J.P. KOKOKU Nos. Sho 43-2603, Sho 43-2604 andSho 45-3828. A mercury lamp used as an ultraviolet source is preferablya high pressure mercury lamp comprising a quartz tube and capable ofemitting ultraviolet rays whose wavelength falls within the range offrom 180 to 320 nm. The ultraviolet irradiation may be performed duringdrawing a substrate, during thermal fixation thereof or after thethermal fixation of the same. If the quality of the substrate is notaffected even when the surface temperature thereof increases up to about150° C., a high pressure mercury lamp whose main wavelength of theemitted light rays is 365 nm can be used as the ultraviolet source. Ifthe substrate requires a low temperature treatment, the ultravioletsource to be used is preferably a low pressure mercury lamp whose mainwavelength of the emitted light rays is 254 nm. Moreover, it is alsopossible to use ozoneless type high pressure mercury lamps and lowpressure mercury lamps.

The corona discharge treatment may be carried out by any conventionallyknown method such as those disclosed in J.P. KOKOKU Nos. Sho 48-5043 andSho 47-51905 and J.P. KOKAI Nos. Sho 47-28067, Sho 49-83767, Sho51-41770 and Sho 51-131576. The discharge frequency ranges from 50 Hz to5000 KHz, preferably 5 KHz to several hundreds of KHz and, inparticular, 10 KHz to 30 KHz. The intensity of treating the substrateusually ranges from 0.001 to 5 KV·A·min/m² and preferably 0.01 to 1KV·A·min/m². The gap clearance between an electrode and a dielectricroll ranges from 0.5 to 2.5 mm and preferably 1.0 to 2.0 mm. Solid StateCorona Treating Machine Model 6KVA available from Pillar Company can beused as an apparatus for the corona discharge treatment.

Moreover, in the flame treatment, a flame source such as natural gasesand liquefied propane gas can be used and it is important to properlycontrol the mixing ratio of these gases to air. A preferred gas/airmixing ratio (by volume) ranges from 1/14 to 1/22, more preferably 1/16to 1/19 for propane; and 1/6 to 1/10, preferably 1/7 to 1/9 for naturalgas.

The flame treatment is preferably carried out to an extent that 1 to 50Kcal/m², more preferably 3 to 20 Kcal/m² is applied to the substrate.Moreover, it is more effective in the flame treatment to limit thedistance between the tip of the inner flame and the substrate to betreated to less than 4 cm.

The glow discharge treatment can be carried out using any conventionallyknown method such as those disclosed in, for instance, J.P. KOKOKU Nos.Sho 35-7578, Sho 36-10336, Sho 45-22004, Sho 45-22005, Sho 45-24040 andSho 46-43480; U.S. Pat. Nos. 3,057,792, 3,057,795, 3,179,482, 3,288,638,3,309,299, 3,424,735, 3,462,335, 3,475,307 and 3,761,299; and U.K.Patent No. 997,093; and J.P. KOKAI No. Sho 53-129262.

Although there has been known a glow discharge treating method in whichthe treatment is carried out while introducing a variety of gases suchas oxygen, nitrogen, helium or argon, but preferred is a glow dischargetreatment performed in the presence of water vapor. The partial pressureof water vapor is preferably not less than 10% and not more than 100%,more preferably not less than 40% and not more than 90%. If the partialpressure is less than 10%, it is difficult to obtain a substrate havingsufficient adhesion to the layers to be applied thereto. The gasatmosphere comprises, in addition to water vapor, air mainly comprisingoxygen and nitrogen.

Further the film to be surface-treated is preferably heated to atemperature preferably not less than 50° C. and not more than Tg, morepreferably not less than 70° C. and not more than Tg, in particular, notless than 90° C. and not more than Tg. The surface temperature of asubstrate in a vacuum can be raised by, for instance, heating with aninfrared heater and heating by bringing the substrate into contact witha hot roll.

The pressure during the glow discharge treatment preferably ranges from0.005 to 20 Torr and more preferably 0.02 to 2 Torr. In addition, thevoltage during the treatment is preferably between 500 and 5000 V, morepreferably between 500 to 3000 V. The discharge frequency used rangesfrom the DC to several thousands of MHz, preferably 50 Hz to 20 MHz andmore preferably 1 KHz to 1 MHz, like the conventional techniques.

The intensity of the discharge treatment of the substrate preferablyranges from 0.01 to 5 KV·A·min/m² and more preferably 0.15 to 1KV·A·min/m² and thus a substrate exhibiting desired adhesion can beobtained.

It is preferred to immediately cool the substrate thus subjected to theglow discharge treatment using a cooling roll to reduce the temperaturethereof.

The surface-treated substrate is then coated with an undercoating layerby the method detailed below. The undercoating layer may be formed bythe single layer or multilayer coating method. A binder mainlycomprising gelatin is preferably used for the coating materials for asecondary undercoating layer in the multilayer application methodcomprising various polymers such as copolymers derived from monomersselected from vinyl chloride, vinylidene chloride, butadiene,methacrylic acid, acrylic acid, itaconic acid and maleic anhydride,polyethyleneimine, epoxy resins, graft gelatin and nitrocellulose.

Polymers as materials for the undercoating layer used in the inventionare, for instance, water-soluble polymers, cellulose esters, latexpolymers and water-soluble polyesters. Specific examples ofwater-soluble polymers are gelatin, gelatin derivatives, casein, agar,sodium alginate, starch, polyvinyl alcohol, polyacrylic acid copolymerand maleic anhydride copolymer; examples of cellulose esters arecarboxymethyl cellulose and hydroxyethyl cellulose. Examples of latexpolymers include vinyl chloride moiety-containing copolymers, vinylidenechloride moiety-containing copolymers, acrylate moiety-containingcopolymers, vinyl acetate moiety-containing copolymers and butadienemoiety-containing copolymers. Among these, most preferred is gelatin.

Examples of compounds capable of swelling the substrate used in theinvention are resorcin, chlororesorcin, methylresorcin, o-cresol,m-cresol, p-cresol, phenol, o-chlorophenol, p-chlorophenol,dichlorophenol, trichlorophenol, monochloroacetic acid, dichloroaceticacid, trifluoroacetic acid, chloral hydrate, with resorcin andp-chlorophenol being preferred.

The undercoating layer used in the invention may comprise various kindsof gelatin-hardening agents.

Examples of gelatin-hardening agents are chromium salts (such as chromealum), aldehydes (such as formaldehyde and glutaraldehyde), isocyanates,active halogen atom-containing compounds (such as2,4-dichloro-6-hydroxy-S-triazine) and epichlorohydrin resins.

The undercoating layer used in the invention may comprise inorganic fineparticles such as SiO₂, TiO₂ and matting agents or may comprisepolymethyl methacrylate copolymer fine particles (particle size: 1 to 10μm) as a matting agent.

The undercoating layer used in the invention can be applied to thesubstrate by any commonly known coating method such as dip coating, airknife coating, curtain coating, roller coating, wire bar coating,gravure coating or the extrusion coating method which makes use of ahopper as disclosed in U.S. Pat. No. 2,681,294. At least two layers may,if desired, be simultaneously coated according to the method disclosedin, for instance, U.S. Pat. Nos. 2,761,791, 3,508,947, 2,941,898 and3,526,528 and Yuji HARASAKI, "Coating Engineerings", p. 253 (1973,published by Asakura Shoten).

In a preferred embodiment of the present invention, the substrate ismade from polyethylene-2,6-naphthalene dicarboxylate which isheat-treated at a temperature ranging from 100 to 115° C. for 24 hours,which has a thickness ranging from 85 to 105 μm, whose surface issubjected to an ultraviolet-irradiation treatment or a glow dischargetreatment; the light-insensitive hydrophilic layer, on the back face, isa gelatin layer having a thickness ranging from 1 to 7 μm and thelight-insensitive hydrophilic layer, on the side of the emulsion layer,is a cellulose binder layer having a thickness ranging from 0.5 to 5 μm.In this respect, the weight ratio of the amount of gelatin in thelight-insensitive hydrophilic layer, on the back face, to that in theemulsion layer on the opposite side preferably ranges from 0.1 to 0.5.

The image-forming method as the third aspect of the present inventionwill be detailed below.

The developer used for developing the light-sensitive material in thepresent invention may comprise currently used additives (such as adeveloping agent, an alkaline agent, a pH-buffering agent, apreservative, a chelating agent). In the development processing of thepresent invention, any known method may be used and any known developingliquid may be used.

The developing agents added to the developer usable in the invention arenot restricted to specific ones, but preferably include, for instance,dihydroxybenzenes, with the combinations of dihydroxybenzenes with1-phenyl-3-pyrazolidones and the combinations of dihydroxybenzenes withp-aminophenols being more preferred, because of their high developingability.

Examples of the dihydroxybenzenes used in the invention arehydroquinone, chlorohydroquinone, isopropylhydroquinone,methylhydroquinone and hydroquinone monosulfonic acid salt, withhydroquinone being particularly preferred.

Examples of 1-phenyl-3-pyrazolidone or derivatives thereof used as thedeveloping agent are 1-phenyl-3-pyrazolidone,1-phenyl-4,4-dimethyl-3-pyrazolidone and1-phenyl-4-methyl-4-hydroxymethyl-3-pyrazolidone.

Examples of p-aminophenolic developing agents used in the invention areN-methyl-p-aminophenol, p-aminophenol, N-(β-hydroxyethyl)-p-aminophenoland N-(4-hydroxyphenyl)glycine, with N-methyl-p-aminophenol beingparticularly preferred.

In general, the dihydroxybenzene type developing agent is preferablyused in an amount ranging from 0.05 to 0.8 mole/l, in particular, 0.2 to0.6 mole/l. If using combinations of dihydroxybenzenes with1-phenyl-3-pyrazolidones or p-aminophenols, the amount of the formerpreferably ranges from 0.05 to 0.6 mole/l, more preferably 0.2 to 0.5mole/l, while the amount of the latter is preferably not more than 0.06mole/l and more preferably not more than 0.03 mole/l.

Examples of the preservatives used in the invention are sodium sulfite,potassium sulfite, lithium sulfite, ammonium sulfite, sodium hydrogensulfite, potassium metabisulfite, formaldehyde sodium bisulfite. Thesulfites are used in an amount of not less than 0.20 mole/l, inparticular, not less than 0.3 mole/l, but the use thereof in an excessamount becomes a cause of the contamination of the developer withsilver. Therefore, the upper limit thereof is desirably 1.2 mole/l.amount thereof particularly preferably ranges from 0.35 to 0.7 mole/l.

As the preservative for the dihydroxybenzene type developing agent, asmall amount of ascorbic acid derivative may be used in combination witha sulfite. Examples of such ascorbic acid derivatives are ascorbic acidand erythorbic acid and alkali metal salts (such as sodium and potassiumsalts) thereof which are stereoisomers of ascorbic acid, with sodiumerythorbate being preferably used because of low cost required for thematerial. The amount of the preservative to be added preferably rangesfrom 0.03 to 0.12 and particularly preferably 0.05 to 0.10 as expressedin terms of molar ratio with respect to the amount of thedihydroxybenzene type developing agent used. If an ascorbic acidderivative is used as the preservative, the developer is preferably freeof any boron compound.

The term "a pH increase observed when 0.1 mole of sodium hydroxide perliter of the developer is not more than 0.25" used herein will bespecifically defined below. The developer is one whose pH is not morethan 10.75 observed when 0.1 mole of sodium hydroxide is added to oneliter of the original developer having a pH of 10.5. The pH increase ismore preferably limited to not more than 0.2.

Examples of alkaline agents used for establishing the desired pH valueare usual water-soluble inorganic alkali metal salts (such as sodiumhydroxide, potassium hydroxide, sodium carbonate and potassiumcarbonate).

Examples of additives other than those explained above are developmentinhibitors such as sodium bromide and potassium bromide; organicsolvents such as ethylene glycol, diethylene glycol, triethylene glycoland dimethylformamide; alkanolamines such as diethanolamine andtriethanolamine; development accelerators such as imidazole andderivatives thereof; and mercapto type compounds, imidazole typecompounds, benzotriazole type compounds and benzimidazole type compoundsas antifoggants or black pepper-inhibiting agents. Specific examples ofsuch antifoggants are 5-nitroindazole, 5-p-nitrobenzoylaminoindazole,1-methyl-5-nitroindazole, 6-nitroindazole, 3-methyl-5-nitroindazole,5-nitrobenzimidazole, 2-isopropyl-5-nitrobenzimidazole,5-nitrobenzotriazole, sodium4-[(2-mercapto-1,3,4-thiadiazol-2-yl)thio]butanesulfonate,5-amino-1,3,4-thiadiazole-2-thiol, methylbenzotriazole,5-methylbenzotriazole and 2-mercaptobenzotriazole. The amount of theseantifoggants in general ranges from 0.01 to 10 mM and preferably 0.1 to2 mM per liter of the developer.

Moreover, the developer used in the invention may further comprisevarious kinds of organic and inorganic chelating agents. Examples ofinorganic chelating agents are sodium tetrapolyphosphate and sodiumhexametaphosphate.

On the other hand, examples of organic chelating agents mainly includeorganic carboxylic acids, aminopolycarboxylic acids, organic phosphonicacids, aminophosphonic acids and organic phosphonocarboxylic acids.

Examples of organic carboxylic acids are acrylic acid, oxalic acid,malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid,succinic acid, azelaic acid, sebacic acid, nonane dicarboxylic acid,decane dicarboxylic acid, undecane dicarboxylic acid, maleic acid,itaconic acid, malic acid, citric acid and tartric acid, but the presentinvention is not restricted to these specific acids.

Examples of aminopolycarboxylic acids are iminodiacetic acid,nitrilotriacetic acid, nitrilotripropionic acid,ethylenediaminemonohydroxyethyl triacetic acid,ethylenediaminetetraacetic acid, glycol ether tetraacetic acid,1,2-diaminopropanetetraacetic acid diethylenetriaminepentaacetic acidtriethylenetriaminehexaacetic acid, 1,3-diamino-2-propanoltetraaceticacid, glycol ether diaminetetraacetic acid and compounds such as thosedisclosed in, for instance, J.P. KOKAI Nos. Sho 52-25632, Sho 55-67747and Sho 57-102624 and J.P. KOKOKU No. Sho 53-40900.

Examples of organic phosphonic acids are hydroxyalkylidene-diphosphonicacids disclosed in, for instance, U.S. Pat. Nos. 3,214,454 and 3,794,591and DEOS No. 2,227,639; and compounds disclosed in, for instance,Research Disclosure, Vol. 181, Item 18170 (May, 1979).

Examples of aminophosphonic acids are amino-tris(methylene phosphonicacid), ethylenediaminetetramethylenephosphonic acid andaminotrimethylenephosphonic acid as well as compounds disclosed in, forinstance, Research Disclosure 18170 described above, J.P. KOKAI Nos. Sho57-208554, Sho 54-61125, Sho 55-29883 and Sho 56-97347.

Examples of organic phosphonocarboxylic acids are compounds disclosedin, for instance, J.P. KOKAI Nos. Sho 52-102726, Sho 53-42730, Sho54-121127, Sho 55-4024, Sho 55-4025, Sho 55-126241, Sho 55-65955 and Sho55-65956 and Research Disclosure 18170 described above.

These chelating agents may be used in the form of alkali metal salts orammonium salts. The amount of these chelating agents preferably rangesfrom 1×10⁻⁴ to 1×10⁻¹, more preferably 1×10⁻³ to 1×10⁻² per liter of thedeveloper.

In addition, the developer may further comprise, as inhibitors forsilver-contamination, compounds disclosed in, for instance, J.P. KOKAINos. Sho 56-24347 and Hei 4-362942 and J.P. KOKOKU Nos. Sho 56-46585 andSho 62-2849.

The developer of the invention may also comprise compounds disclosed inJ.P. KOKAI No. Sho 62-212651 as uneven development-inhibiting agents;and compounds disclosed in J.P. KOKAI No. Sho 61-267759 as auxiliaryagents for solubilization.

Moreover, the developer may comprise, if necessary, color tone-adjustingagents, surfactants, antifoamers, film-hardening agents or the like.

The developer used in the invention comprises, as buffering agents,boric acid as disclosed in J.P. KOKAI No. Sho 62-186259; sugars asdisclosed in J.P. KOKAI No. Sho 60-93433 (such as saccharose); oximes(such as acetoxime); phenols (such as 5-sulfosalicylic acid); andtertiary phosphoric acid salts (such as sodium and potassium salts),with carbonates and boric acid being preferably used.

The pH value of the developer preferably ranges from 9.5 to 11.0,particularly preferably 9.8 to 10.7.

The developing temperature and time correlate to one another and aredetermined depending on the overall processing time. In general, thedeveloping temperature ranges from about 20 to about 50° C., preferably25 to 45° C. and the developing time ranges from 5 seconds to 2 minutes,preferably 7 seconds to 1 minute and 30 seconds.

When processing a silver halide monochromatic photographiclight-sensitive material, the amount of the developer to be supplementedis not more than 225 ml and preferably not more than 180 ml per onesquare meter of the material.

It is preferred to concentrate processing solutions and to dilute themprior to practical use for the purposes of saving cost required fortransportation and packing materials and for reducing the space requiredfor storing. It is effective to use potassium salts as the saltscomponents of the developer in order to concentrate the developer.

The fixing solution used in the fixing process of the present inventionis an aqueous solution containing sodium thiosulfate, ammoniumthiosulfate and, if necessary, tartaric acid, citric acid, gluconicacid, boric acid, iminodiacetic acid, 5-sulfosalicylic acid,glucoheptanoic acid, tiron, ethylenediaminetetraacetic acid,diethylenetriaminepentaacetic acid, nitrilotriacetic acid and/or saltsthereof. The developer is preferably free of boric acid from theviewpoint of the recent environmental protection.

The fixing agents in the fixing solution used in the invention may besodium thiosulfate and ammonium thiosulfate. Ammonium thiosulfate ispreferred from the viewpoint of its fixing rate, but sodium thiosulfatemay be used from the viewpoint of the recent environmental protection.The amount of these known fixing agents may properly be changed and ingeneral ranges from about 0.1 to about 2 molesll, particularlypreferably 0.2 to 1.5 mole/l.

The fixing solution may, if desired, comprise a film-hardening agent(such as a water-soluble aluminum compound), a preservative (such as asulfite or bisulfite), a pH-buffering agent (such as acetic acid), apH-adjusting agent (such as ammonia or sulfuric acid), a chelatingagent, a surfactant, a wetting agent and/or a fixing accelerator.

Examples of surfactants are anionic surfactants such as sulfated andsulfonated products; polyethylene type surfactants; and amphotericsurfactants as disclosed in J.P. KOKAI No. Sho 57-6740. Moreover, aknown antifoamer may be added to the fixing solution. Examples ofwetting agents are alkanolamines and alkylene glycols. Examples offixing accelerators are thiourea derivatives as disclosed in J.P. KOKOKUNos. Sho 45-35754, Sho 58-122535 and Sho 58-122536; alcohols eachcarrying a triple bond in the molecule; thio ether compounds asdisclosed in U.S. Pat. No. 4,126,459; and meso-ionic compounds asdisclosed in J.P. KOKAI No. Hei 4-229860; as well as compounds asdisclosed in J.P. KOKAI No. Hei 2-44355.

Moreover, examples of pH-buffering agents include organic acids such asacetic acid, malic acid, succinic acid, tartaric acid, citric acid,oxalic acid, maleic acid, glycolic acid and adipic acid; and inorganicbuffering agents such as boric acid, phosphoric acid salts and sulfites,with acetic acid, tartaric acid and sulfites being preferred.

In this respect, the pH-buffering agent is used for preventing anyincrease in the pH of the fixing solution due to the developer broughtinto the fixing solution and the amount thereof to be used preferablyranges from 0.01 to 1.0 mole/l and more preferably 0.02 to 0.6 mole/l.

The pH value of the fixing solution preferably ranges from 4.0 to 6.5and, in particular, 4.5 to 6.0.

The fixing solution may likewise comprise a dye-liquation acceleratorsuch as those disclosed in J.P. KOKAI No. Sho 64-4739.

Examples of film-hardening agent in the fixing solution used in theinvention are water-soluble aluminum compounds and chromium salts.Preferred examples thereof are water-soluble aluminum compounds such asaluminum chloride, aluminum sulfate and potassium alum. The added amountthereof preferably ranges from 0.01 to 0.2 mole/l and more preferably0.03 to 0.08 mole/l.

The fixing temperature ranges from about 20 to about 50° C., preferably25 to 45° C. and the fixing time ranges from 5 seconds to one minute andpreferably 7 to 50 seconds.

The amount of the fixing solution to be supplemented is not more than600 ml, in particular, not more than 500 ml per unit amount (1 m²) ofthe processed light-sensitive material.

After the developing and fixing treatments, the light-sensitive materialis then washed with water or subjected to a stabilization treatment.

In the water-washing or stabilization treatment, the amount of requiredwater is in general not more than 20 1 per unit amount (1 m²) of theprocessed silver halide light-sensitive material or the treatment can becarried out while reducing the amount thereof to be supplemented to notmore than 3 l (including 0, i.e., water-washing with saved up water). Inother words, this permits the water-saving process and elimination ofthe need for piping works for establishing an automatic developingmachine.

As a method for reducing the amount of washing-water, there has longbeen known a multistage countercurrent system (such as 2-stage and3-stage systems). If the multistage countercurrent system is applied tothe present invention, the light-sensitive material after the fixingtreatment gradually moves towards the normal direction, i.e., stepwisecomes in contact with the processing solution which is not contaminatedwith the fixing solution and thus the light-sensitive material is moreeffectively water-washed.

If the material is washed with a small amount of water, it is morepreferred to provide washing baths for squeeze rollers and cross-overrollers such as those disclosed in J.P. KOKAI Nos. Sho 63-18350 and Sho62-287252. Moreover, addition of various kinds of oxidizing agentsand/or filtration through a filter may be combined with these means inorder to reduce the degree of environmental pollution encountered whenwashing with a small amount of water.

A part or the whole of the overflow liquid from a water-washing orstabilization bath may be used in the processing liquid having an fixingability in the preceding process as disclosed in J.P. KOKAI No. Sho60-235133. In this respect, the overflow liquid is generated bysupplementing water provided with a mildewproof means to thewater-washing or stabilization bath in proportion to the quantity ofprocessed light-sensitive material in the method of the presentinvention.

The washing liquid may comprise a water-soluble surfactant and/or anantifoamer in order to prevent the occurrence of uneven foaming whichmay often be caused during washing with a small amount of water and/orto prevent any transfer of the components of the processing agent,adhered to the squeeze rollers, to the processed film.

In addition, a dye-absorber as disclosed in J.P. KOKAI No. Sho 63-163456can be added to the water-washing bath to prevent any contamination ofthe light-sensitive material with the dye released from the material.

The light-sensitive material may be subjected to a stabilizationtreatment subsequent to the foregoing water-washing. In this case, it ispossible to use, for instance, a bath which comprises compounds asdisclosed in J.P. KOKAI Nos. Hei 2-201357, Hei 2-132435, Hei 1-102553and Sho 46-44446 as a final treating bath for the light-sensitivematerial.

The stabilization bath may optionally comprise an ammonium compound, ametallic compound of, for instance, Bi or Al, a fluorescent brightener,various kinds of chelating agents, a film pH-adjusting agent, afilm-hardening agent, a bactericide, a mildewproofing agent,alkanolamine and/or a surfactant. Water used in the water-washing and/orstabilization processes may preferably be tap water, deionized water orwater sterilized by the use of a halogen lamp, a UV bactericidal lamp orvarious oxidizing agents (such as ozone, hydrogen peroxide andchlorates), or may be washing water comprising compounds disclosed inJ.P. KOKAI Nos. Hei 4-39652 and Hei 5-241309.

In the water-washing or stabilization process, the processingtemperature and time preferably range from 0 to 50° C. and 5 seconds to2 minutes, respectively.

The processing liquid used in the invention is preferably stored whilepacking in a low oxygen-permeable packing material disclosed in J.P.KOKAI No. Sho 61-73147.

If reducing the amount of the processing solution to be supplemented, itis preferred to prevent any evaporation of the processing solution andthe oxidation thereof with air by reducing the contact area between thesolution with the air in the processing bath. Roller-conveying automaticdeveloping machines are disclosed in, for instance, U.S. Pat. Nos.3,025,779 and 3,545,971 and are simply referred to as roller-conveyingtype processor in this specification. The roller-conveying typeprocessor comprises four steps, i.e., developing, fixing, water-washingand drying steps and the method of the invention most preferablycomprises these four steps although the use of other steps (such asstopping step) is not excluded. A stabilization step may be substitutedfor the water-washing step.

The solid processing agent used in the invention may be in any shapesuch as powder, tablet, granule, mass or paste, with the shape disclosedin J.P. KOKAI No. Sho 61-259921 or tablet being preferred. Tablets canbe prepared by general methods disclosed in, for instance, J.P. KOKAINos. Sho 51-61387, Sho 54-155038 and Sho 52-88025 and U.K. Patent No.1,213,808; granular processing agents can be prepared by general methodsdisclosed in, for instance, J.P. KOKAI Nos. Hei 2-109042, Hei 2-109043,Hei 3-39735 and Hei 3-39739; and powdery processing agent can beprepared by general methods disclosed in, for instance, J.P. KOKAI No.Sho 54-133332, U.K. Patent Nos. 725,892 and 729,862 and German PatentNo. 3,733,861.

The bulk density of the solid processing agent preferably ranges from0.5 to 6.0 g/cm³, in particular, 1.0 to 5.0 g/cm³ from the viewpoint ofits solubility and the intended effect of the present invention.

In the passage "solid processing agent which comprises at least twomutually reactive particulate substances; these two reactive substancesare arranged such that layers of these two reactive substances adjacentto one another are isolated through at least one interposed separatinglayer which comprises a substance inert to these layers of the reactivesubstances adjacent to one another; a bag allowing vacuum packaging isused as a packing material; and the solid processing agent is sealed inthe exhausted bag", the term "inert" herein means that the substances donot undergo any reaction under the usual conditions in the package whenthese substances physically come in contact with one another, or thatsome reaction takes place, but they do not undergo any severe reaction.It is sufficient that the two reactive substances are inert in theintended applications due to the presence of the inert substance,irrespective of the fact that the latter is inert to these twosubstances reactive with one another. Moreover, the inert substance is amaterial simultaneously used along with these reactive two substances.For instance, hydroquinone and sodium hydroxide undergo a reaction whenthey directly come in contact with one another in a developer, but theycan be stored over a long time period within a vacuum package throughthe use of, for instance, sodium sulfite as a layer for separating thesehydroquinone and sodium hydroxide layers. Examples of packing materialsused for vacuum-packaging these substances are bags made from inertplastic materials or a laminates of plastic materials and metal foils.

Various kinds of additives used in the light-sensitive material and theimage-forming method of the invention are not restricted to specificones and those disclosed in the related parts of the following articlescan, for instance, preferably be used in the invention.

    ______________________________________                                        Item      Related Passages                                                    ______________________________________                                        1)  Silver Halide                                                                           J. P. KOKAI No. Hei 2-97937 (passage extend-                        Emulsion  ing from the right lower column, line 12 on                         and       page 20 to the left lower column, line 14                           Methods for                                                                             on page 21); J. P. KOKAI No. Hei 2-12236                            Preparing (passage extending from the right upper                             the Same  column, line 19 on page 7 to right lower                                      column, line 12 on page 8); Japanese Patent                                   Appln. Serial Nos. Hei 3-116573 and Hei 3-                                    189532.                                                         2)  Spectral  J. P. KOKAI No. Hei 2-55349 (passage extending                      Sensiti-  from the left upper column, line 8 on page 7 to                     zing      right lower column, line 8 on page 8); J. P. KOKAI                  Dyes      No. Hei 2-39042 (passage extending from the right                             lower column, line 8 on page 7 to right lower                                 column, line 5 on page 13); J. P. KOKAI No. Hei 2-                            12235 (passage extending from the left lower                                  column, line 13 to right lower column, line 4 on                              page 8); J. P. KOKAI No. Hei 2-103536 (passage ex-                            tending from the right lower column, line 3 on                                page 16 to left lower column, line 20 on page                                 17); J. P. KOKAI Nos. Hei 1-112235; Hei 2-124560                              and Hei 3-7928 and Japanese Patent Appln. Serial                              Nos. Hei 3-189532 and Hei 3-411064.                             3)  Surfac-   J. P. KOKAI No. Hei 2-12236 (passage extending                      tants &   from the right upper column, line 7 to right                        Anti-     lower column, line 7 on page 9; J. P. KOKAI No.                     static    Hei 2-18542 (passage extending from the left                        agent     lower column line 13, on page 2 to right lower                                column, line 18 on page 4                                       4)  Compounds J. P. KOKAI No. Hei 2-103536 (passage extending                     Having    from the right lower column, line 6 on page 18                      Acid      to left upper column, line 1 on page 19); and                       Groups    J. P. KOKAI No. Hei 2-55349 (passage extending                                from the right lower column, line 13 on page 8                                to left upper column, line 8 on page 11.                        5)  Antifog-  thiosulfone compounds disclosed in J. P. KOKAI                      gants     No. Hei 2-103536 (passage extending from the                                  right lower column, line 19 on page 17 to right                               upper column, line 4 on page 18; and passage                                  extending from the right lower column, lines 1                                to 5 on page 18); and J. P. KOKAI No. Hei 1-                                  237538.                                                         6)  Poly-     J. P. KOKAI No. Hei 2-55349 (passage extending                      hydroxy-  from left upper column, line 9 to right lower                       benzenes  column, line 17 on page 11.                                     7)  Matting   J. P. KOKAI No. Hei 2-103536 (passage extend-                       Agent,    ing from the left upper column, line 15 to                          Slipping  right upper column, line 15 on page 19.                             Agents and                                                                    Plasticizers                                                              8)  Film-     J. P. KOKAI No. Hei 2-103536 (passage appearing in                  Hardening the right upper column, lines 5 to 17 on page                       Agents    18).                                                            9)  Dyes      Solid Dyes disclosed in J. P. KOKAI No.                                       Hei 2-103536 (passage appearing in the right                                  lower column, lines 1 to 18 on page 17);                                      J. P. KOKAI No. Hei 2-39042                                                   (passage extending from the right upper column, line                          1 on page 4 to right upper column, line 5 on page 6);                         J. P. KOKAI No. Hei 2-294638 and Japanese Patent                              Appln. Serial No. Hei 3-185773.                                 10) Tetrazo-  J. P. KOKAI No. Hei 2-39143 (passage extending                      lium      from left lower column, line 8 on page 4 to                         Compounds left lower column, line 6 on page 6); J. P.                                   KOKAI No. Hei 3-123346 (passage extending from                                right upper column, line 19 on page 3 to left                                 upper column, line 20 on page 5).                               11) Redox     J. P. KOKAI No. Hei 2-301743 (compounds repre-                      Compounds sented by the general formula (I) (in particular                              Compounds 1 to 50); J. P. KOKAI No. Hei 3-174143                              (Compounds 1 to 75 represented by the general                                 formulas (R-1), (R-2) and (R-3) appearing on                                  page 3 to 20); and compounds disclosed in Japa-                               nese Patent Appln. Serial Nos. Hei 3-69466 and                                Hei 3-15648.                                                    12) Mono-     J. P. KOKAI No. Hei 2-287532 (compounds represen-                   methine   ted by the general formula (II) (in particular,                     Compounds illustrated Compounds II-1 to II-26)).                          13) Colloidal J. P. KOKAI No. Hei 4-214551 (Compounds disclo-                     Silica    sed in Paragraph No. [0005])                                    14) Developers                                                                              J. P. KOKAI No. Hei 2-103536 (passage extending                     and       from the right upper column, line 16 on page                        Developing                                                                              19 to left upper column, line 8 on page 21);                        Methods   J. P. KOKAI No. Hei 2-55439 (passage extending                                from right lower column, line 1 on page 13 to                                 left upper column, line 10 on page 16.                          15) Latex     J. P. KOKAI No. Hei 2-103536 (passage appearing                     polymer   in the left lower column, lines 12 to 20 on                                   page 18.                                                        16) Binders   J. P. KOKAI No. Hei 2-18542 (passage appearing                                in the right lower column, lines 1 to 20                                      on page 3.                                                      17) Hydrazine J. P. KOKAI No. Hei 2-12236 (passage extending                      Nucleating                                                                              from right upper column, line 19 on page 2 to                       Agents    right upper column, line 3 on page 7); J. P.                                  KOKAI No. Hei 3-174143 (passage extending from                                right lower column, line 1 on page 20 to right                                upper column, line 20 on page 27): general                                    formula (II) and illustrated compounds II-1 to                                II-54.                                                          18) Hydrazine J. P. KOKAI No. Hei 2-103536 (compounds repre-                      Nucleating                                                                              sented by the general formula (II-m) to (II)-p                      Accelera- and illustrated Compounds II-1 to II-22;                            tors      Compounds disclosed in J. P. KOKAI No. Hei 1-                                 179939.                                                         19) Black     Compounds disclosed in U.S. Pat. No.                                pepper    4,956,257 and J. P. KOKAI No. Hei 1-118832.                         Inhibitory                                                                    Agent                                                                     20) Dihydroxy-                                                                              Compounds disclosed in J. P. KOKAI No. Hei 2-                       benzenes  3-39948 and EP 452772A.                                         ______________________________________                                    

The present invention will hereinafter be described in more detail withreference to the following non-limitative working Examples and theeffects practically attained by the present invention will also bediscussed in detail in comparison with Comparative Examples.

EXAMPLE 1 Preparation of Core (polybutadiene homopolymer)/Shell(styrene/2-acetoacetoxyethyl methacrylate (84/16)) Latex (core/shellratio: 50/50) (Preparation of Illustrated Compound P-17)

To a 1 l volume three-necked flask equipped with a stirring machine anda reflux condenser, there were added 0.28 g of sodium hydrogen sulfite,3.52 g of a 1 mole/l solution of sodium hydrogen carbonate and 454 g ofdistilled water, followed by dissolution with stirring, addition of294.1 g of a polybutadiene latex (particle size: 112 nm; solid content:34.3% by weight; available from Nippon Zeon Co., Ltd. under the tradename of LX-111J) and heating, with stirring, at 65° C. in a nitrogen gasstream.

After adding a solution prepared by dissolving 0.32 g of potassiumpersulfate in 20 g of distilled water, the dropwise addition of a mixedsolution containing 84.0 g of styrene and 16.0 g of 2-acetoacetoxyethylmethacrylate and a solution of 0.16 g of potassium persulfate in 50 g ofdistilled water were initiated at a constant rate in such a manner thatthe dropwise addition of each solution was completed within 1.5 hour.

After completion of the dropwise addition, the reaction system washeated for one hour with stirring, followed by addition of a solution of0.16 g of potassium persulfate in 20 g of distilled water and heatingfor additional 3 hours with stirring.

The reaction system was cooled to room temperature and then filtered togive 931.4 g of a desired core/shell latex (solid content: 21.2%; yieldof solid content: 98.3%; averaged particle size as determined by CoulterSubmicron Analyzer (available from Nikkaki Co., Ltd.): 138 nm).Moreover, a part of the resulting latex (100 g) was lyophilized to give20.2 g of core/shell fine powder of the present invention.

EXAMPLE 2 Preparation of Core (polybutadiene homopolymer)/Shell (n-butylacrylate/2-acetoacetoxyethyl methacrylate (84/16)) Latex (core/shellratio: 50/50) (Preparation of Illustrated Compound P-19)

To a 1 l volume three-necked flask equipped with a stirring machine anda reflux condenser, there were added 0.28 g of sodium hydrogen sulfite,3.52 g of a 1 mole/l solution of sodium hydrogen carbonate and 454 g ofdistilled water, followed by dissolution with stirring, addition of294.1 g of a polybutadiene latex (particle size: 112 nm; solid content:34.3% by weight; available from Nippon Zeon Co., Ltd. under the tradename of LX-111J) and heating, with stirring, at 65° C. in a nitrogen gasstream.

After adding a solution prepared by dissolving 0.32 g of potassiumpersulfate in 20 g of distilled water, the dropwise addition of a mixedsolution containing 84.0 g of n-butyl acrylate and 16.0 g of2-acetoacetoxyethyl methacrylate and a solution of 0.16 g of potassiumpersulfate in 50 g of distilled water were initiated at a constant ratein such a manner that the dropwise addition of each solution wascompleted within 1.5 hour.

After completion of the dropwise addition, the reaction system washeated for one hour with stirring, followed by addition of a solution of0.16 g of potassium persulfate in 20 g of distilled water and heatingfor additional 3 hours with stirring.

The reaction system was cooled to room temperature and then filtered togive 931.0 g of a desired core/shell latex (solid content: 21.0%; yieldof solid content: 97.3%; particle size: 145 nm).

Electron micrographs of the latex polymeres prepared in Examples 1 and 2are shown in FIGS. 1 and 2 (FIG. 1 is an electron micrograph of theillustrated polymer P-17, while FIG. 2 shows that of the illustratedpolymer P-19).

The magnifying factor of these micrographs is 100,000 and therefore, alength of 1 cm on the micrograph corresponds to 0.1 μm.

The light and shade contrast of the latex particles was made clear bystaining (with osmium oxide) double bonds remaining on the butadienepolymer and the dark portion corresponds to the core polymer while thebright portion corresponds to the shell polymer.

As seen from FIGS. 1 and 2, it is clear that the conjugated dienepolymer cores are certainly covered with the active methylene-carryingmonomer moiety-containing shell polymer in both of the latexes, that thedesired core/shell polymer is formed and that any separate particlescomprising only the shell-forming polymer are not present at all.

EXAMPLE 3

Other core/shell latexes (the foregoing illustrated compounds P-1 to 33)were synthesized according to basically the same method used in Examples1 and 2.

A part of these core/shell latexes were inspected for the particle size.The results thus obtained are listed in the following Table 1 along withthe particle size of the original core latexes and the core/shell latexparticle size theoretically predicted from the core/shell weight ratio.

                  TABLE 1                                                         ______________________________________                                                          Particle Size (nm)                                          Poly- Core/Shell Ratio                                                                          Core Polymer                                                                              Core/Shell                                                                           Core/Shell                               mer   (by weight) (found)     (found)                                                                              (calc.)                                  ______________________________________                                        P-2   50/50       136         173    171                                      P-3   50/50       136         168    171                                      P-4   50/50       136         170    171                                      P-6   67/33       136         156    150                                      P-7   75/25       136         150    146                                      P-12  50/50       136         168    171                                      P-17  50/50       112         138    141                                      P-19  50/50       112         165    141                                      P-26  50/50       173         211    218                                      P-29  50/50       197         239    248                                      ______________________________________                                         Note: Each core/shell (calculated) value is determined by calculating the     increase in the volume based on the core/shell weight ratio while assumin     that the specific gravities of the core and shell polymers are identitica     to one another. Therefore, if there is a difference in specific gravities     there may be a slight difference between the values calculated and found.

The data listed in Table 1 clearly indicate that each latex of thepresent invention shows an increase in the particle size almostidentical to the calculated value, during the process for converting thecore latex into the core/shell latex and this in turn indicates that thelatex does not comprise any core latex free of the shell polymer andparticles comprising only the shell polymer and that the latex has adesired core/shell latex structure and is almost free of, for instance,aggregation during the polymerization process.

EXAMPLE 4

To a 6% by weight gelatin solution obtained by dissolving gelatin at 40°C., there was added each latex polymer of the present invention listedin the following Table 2 such that the polymer content of the resultingmixture was 50 or 75% by weight on the basis of the solid content of thegelatin solution, followed by addition of1,2-bis(vinylsulfonylacetamido)ethane as a film-hardening agent in anamount of 12 mM per 100 g of gelatin and sodium dodecylbenzenesulfonateas an auxiliary agent for coating in an amount of 1 g/one liter of thegelatin solution and addition of sodium polystyrenesulfonate as athickener in such an amount that the the resulting gelatin solution hasa viscosity of 30 cp to give a coating solution. The coating solutionwas applied onto the surface of a polyethylene terephthalate substrate(thickness: 100 μm) on which a subbing layer had been applied in acoated amount of 5 g/m² and then dried. After storing these samples at25° C. and 55% RH for one week, the strength of each wet film wasevaluated by the following method.

Method for Evaluating Strength of Wet Film

Each sample was immersed in distilled water maintained at 38° C. for 2minutes, a sapphire needle having a radius of 0.3 mm was attached to thesample film surface under pressure, followed by continuously increasingthe load applied to the needle while moving the needle at a speed of 10mm/sec to determine the load (g) required for breaking the film. Theresults are listed in the following Table 2.

                  TABLE 2                                                         ______________________________________                                              Added   Kind and Content of                                                                            Strength of                                    Poly- Amount  Active   Methylene                                                                             Wet Film                                       mer   (wt %.sup.1))                                                                         Monomer  (wt %.sup.1))                                                                         (g)     Remarks                                ______________________________________                                        P-2   50      M-1      2       120     Invention                              P-3   50      M-1      4       155     Invention                              P-4   50      M-1      8       220     Invention                              P-4   75      M-1      8       210     Invention                              P-6   50      M-1      5.3     205     Invention                              P-7   50      M-1      4       170     Invention                              P-10  50      M-1      8       170     Invention                              P-10  75      M-1      8       155     Invention                              P-12  50      M-3      8       175     Invention                              P-16  50      M-8      8       170     Invention                              P-17  50      M-1      8       210     Invention                              P-20  50      M-2      8       195     Invention                              P-22  50      M-18     8       180     Invention                              P-23  50      M-1      1.6     135     Invention                              P-28  50      M-7      9       200     Invention                              P-30  50      M-1      10      185     Invention                              P-34  50      yellow   monomer 10                                                                            115     Invention                                            coupler                                                         A-1   50      --       0       80      Comparison                             A-2   50      --       0       78      Comparison                             A-3   50      M-1      4       90      Comparison                             A-4   50      M-1      8       120     Comparison                             A-5   50      M-1      16      145     Comparison                             A-5   75      M-1      16      128     Comparison                             A-6   50      M-1      35      155     Comparison                             A-7   50      M-1      8       125     Comparison                             A-8   50      M-1      10      130     Comparison                             A-9   50      yellow   monomer 18                                                                            110     Comparison                                           coupler                                                         A-10  50      yellow   monomer 10                                                                            100     Comparison                             coupler       coupler                                                         Not    0      --       --      180     Comparison                             Added                                                                         ______________________________________                                    

The comparative latex compounds used for proving the effects of thecore/shell latexes of the present invention and the compound P-34 of thepresent invention were prepared as follows:

Comparative Compound A-1: polybutyl acrylate latex

Comparative Compound A-2: (styrene/butadiene (37/63)) latex copolymer

Comparative Compounds A-3 to A-8

The following latexes free of the core/shell structure (monolayer typeones) were synthesized according to the disclosure of J.P. KOKOKU No.Sho 45-5819.

A-3: butyl acrylate/2-acetoacetoxyethyl methacrylate (M-1) (96/4: weightratio)

A-4: butyl acrylate/M-1 (92/8)

A-5: butyl acrylate/M-1 (88/16)

A-6: butyl acrylate/M-1 (65/35)

A-7: styrene/butadiene/M-1 (30/62/8)

A-8: butyl acrylate/M-1/acrylic acid (75/15/10)

The following core/shell type yellow polymer coupler latexes weresynthesized according to the method disclosed in J.P. KOKAI No. Sho58-42044.

Comparative Compounds A-9, 10: core butyl acrylate; shell: ##STR2## A-9:core/shell=9.1/90.9 A-10: core/shell=50/50

Compound P-34 of the Present Invention:

core: styrene/butadiene (37/63) copolymer

shell: ##STR3##

The results listed in Table 2 indicate that the polymer of the presentinvention having active methylene groups in the shell portion ensuresfilm strength higher than that achieved by the non-core/shell typepolymer having the same active methylene monomer content, irrespectiveof the added amount of the latexes and the comparison of P-34 with A-10indicates that the latex of the present invention also ensures filmstrength higher than that achieved by the conventional latex due to thepresence of the conjugated diene monomer in the core portion, althoughthese latexes are the same core/shell type ones. These results clearlyindicate that distinct core/shell structures are formed in the latexpolymeres of the present invention and that the latex polymeres of theinvention are quite useful.

EXAMPLE 5 Preparation of Core/Shell Latex (core: ethylene glycoldimethacrylate/n-butyl acrylate (20/80); shell: n-butyl acrylate/M-1(84/16); core/shell ratio: 50/50) (Preparation of the illustratedcompound P-51)

To a 2 l volume three-necked flask equipped with a stirring machine anda reflux condenser, there were added 0.576 g of sodium hydrogen sulfite,1.50 g of sodium di-n-hexyl succinate monosulfonate, 30.0 g of ethyleneglycol dimethacrylate, 120 g of n-butyl acrylate and 510 g of distilledwater, followed by heating, with stirring, at 50° C. in a nitrogen gasstream.

After adding an initiator solution comprising 0.5 g of potassiumpersulfate, 3.7 g of 1N aqueous sodium hydrogen carbonate and 30 g ofwater and heating for 30 minutes with stirring, an initiator solutioncomprising 1.0 g of potassium persulfate, 7.4 g of a 1N aqueous sodiumhydrogen carbonate and 60 g of water was added followed by heating, withstirring, at 50° C. for 2 hours and then at 90° C. for 3 hours to give acore latex (averaged particle size as determined by Coulter SubmicronAnalyzer (available from Nikkaki Co., Ltd.): 126 nm).

To the resulting core latex, there was added a solution of 0.65 g ofsodium hydrogen sulfite in 250 g of distilled water and then thetemperature of the contents of the flask was adjusted to 70° C. A mixedsolution comprising 126 g of n-butyl acrylate and 24 g of2-acetoacetoxyethyl methacrylate and an aqueous solution comprising1.125 g of potassium persulfate, 8.25 g of a 1N aqueous sodium hydrogencarbonate solution and 150 g of distilled water were prepared and theywere dropwise added to the core latex solution at a constant rate sothat the dropwise addition was completed within one hour. Aftercompletion of the dropwise addition, the reaction system was heated to70° C. for one hour with stirring, followed by addition of a solution of0.375 g of potassium persulfate in 50 g of distilled water and heating,with stirring, at 85° C. for 3 hours.

The reaction solution was cooled and filtered to give 1355 g of anintended latex, P-51, of the present invention. The resulting latex hada solid content concentration of 21.30% (yield of solid content: 96.2%)and a particle size of 159 nm.

EXAMPLE 6 Preparation of Core/Shell Latex (core: n-dodecyl methacrylate;shell: styrene/M-1 (84/16); core/shell ratio: 50/50) (Preparation of theillustrated compound P-41)

To a 2 l volume three-necked flask equipped with a stirring machine anda reflux condenser, there were added 150 g of n-dodecyl methacrylate,3.0 g of sodium di-n-hexyl succinate monosulfonate, 14.8 g of a 1Naqueous sodium hydrogen carbonate, 510 g of distilled water and 200 mlof methanol and the mixture was heated, with stirring, at 80° C. in anitrogen gas stream.

To the mixture, there were added, four times, an initiator solutioncomprising 0.5 g of potassium persulfate and 30 g of distilled water atintervals of 2 hours to carry out emulsion polymerization. Aftercompleting the addition of the final initiator solution, the methanolwas distilled off over 3 hours to give a core latex (particle size: 263nm).

To the resulting core latex, there was added a solution of 0.65 g ofsodium hydrogen sulfite in 300 g of distilled water and then thetemperature of the contents of the flask was adjusted to 70° C. A mixedsolution comprising 126 g of styrene and 24 g of 2-acetoacetoxyethylmethacrylate and an aqueous solution comprising 1.125 g of potassiumpersulfate, 8.25 g of a 1N aqueous sodium hydrogen carbonate solutionand 150 g of distilled water were prepared and they were dropwise addedto the core latex solution at a constant rate such that the dropwiseaddition was completed within one hour. After completion of the dropwiseaddition, the reaction system was heated to 70° C. for one hour withstirring, followed by addition of a solution of 0.375 g of potassiumpersulfate in 50 g of distilled water and heating, with stirring, at 85°C. for 3 hours.

The reaction solution was cooled and filtered to give 1375 g of anintended latex, P-41, of the present invention. The resulting latex hada solid content concentration of 21.45% (yield of solid content: 98.3%)and a particle size of 336 nm.

Moreover, a part of the resulting latex (100 g) was lyophilized to give20.7 g of powder comprising core/shell fine particles.

Other illustrated compounds could be prepared by methods according tothose used in Example 5. In Example 5, the particle size of the corelatex and that of the core/shell latex are in good agreement with thosepredicted on the basis of the weight ratio of the core and shellpolymers and this clearly indicates that the resulting latexes aresubstantially free of any aggregation and formation of particles otherthan the core/shell type ones.

EXAMPLE 7

A conductive layer and a backing layer each having the followingcomposition were simultaneously coated on one side of a biaxiallyoriented polyethylene terephthalate substrate (thickness: 100 μm)provided with undercoating layers on both sides thereof.

    ______________________________________                                        [Conductive Layer]                                                            SnO.sub.2. /Sb (9/1 (weight ratio); average particle                                                  200    mg/m.sup.2                                     size: 0.25μ)                                                               gelatin (Ca.sup.++   content: 3000 ppm)                                                               77     mg/m.sup.2                                     Compound-6              7      mg/m.sup.2                                     sodium dodecylbenzenesulfonate                                                                        10     mg/m.sup.2                                     sodium dihexyl-α-sulfosuccinate                                                                 40     mg/m.sup.2                                     sodium polystyrenesulfonate                                                                           9      mg/m.sup.2                                     [Backing Layer]                                                               gelatin (Ca.sup.++   content: 30 ppm)                                                                 2.82   g/m.sup.2                                      poly(methyl methacrylate) fine particles                                                              20     mg/m.sup.2                                     (average particle size: 4.0 μm)                                            Compound-1              3      mg/m.sup.2                                     Compound-2              40     mg/m.sup.2                                     Compound-3              40     mg/m.sup.2                                     Compound-4              80     mg/m.sup.2                                     Compound-5              150    mg/m.sup.2                                     sodium dodecylbenzenesulfonate                                                                        75     mg/m.sup.2                                     sodium dihexyl-α-sulfosuccinate                                                                 20     mg/m.sup.2                                     Compound-6              5      mg/m.sup.2                                     sodium sulfate          50     mg/m.sup.2                                     sodium acetate          85     mg/m.sup.2                                     1,2-bis(vinylsulfonylacetamide)ethane                                                                 150    mg/m.sup.2                                     ______________________________________                                        Compound-1                                                                     ##STR4##                                                                     Compound-2                                                                     ##STR5##                                                                     Compound-3                                                                     ##STR6##                                                                     Compound-4                                                                     ##STR7##                                                                     Compound-5                                                                    C.sub.8 F.sub.17 SO.sub.3 Li                                                  Compound-10                                                                    ##STR8##                                                                     Compound-6                                                                     ##STR9##                                                                       Then the following emulsion layer and upper and lower protective layers 

[Emulsion Layer]

To an aqueous gelatin solution maintained at 40° C. and containing5,6-cyclopentane-4-hydroxy-1,3,3a,7-tetrazaindene (5×10⁻³ mole per moleof silver), there were simultaneously added an aqueous silver nitratesolution and an aqueous sodium chloride solution containing (NH₄)₂ Rh(H₂O)Cl₅ in an amount of 4×10⁻⁵ mole per mole of silver over 7 minutes,while controlling the voltage to 95 mV during the addition to preparecore particles having a particle size of 0.12 μm. Thereafter, there wereadded, to the foregoing reaction system, an aqueous silver nitratesolution and an aqueous sodium chloride solution containing (NH₄)₂ Rh(H₂O)Cl₅ in an amount of 1.2×10⁻⁴ mole per mole of silver over 14 minutes,while controlling the voltage to 95 mV during the addition to preparesilver chloride cubic particles having an average particle size of 0.15μm.

To the resulting emulsion, there were added 50 mg/m² of the compoundrepresented by the formula: C₁₆ H₃₃ O(CH₂ CH₂ O)₂₅ H, 24 mg/m² of5,6-cyclopentane-4-hydroxy-1,3,3a,7-tetrazaindene, 5 mg/m² of5-methyltriazole, 3 mg/m² of Compound-6, a latex polymer (kinds andamounts are listed in the following Table 3) and 126 mg/m² of2-bis(vinylsulfonylacetamide)ethane as a film-hardening agent and theresulting emulsion was applied to the substrate in such an amount thatthe coated amounts of silver and gelatin were 3.0 mg/m² and 1.1 g/m²,respectively.

    ______________________________________                                        [Lower Protective Layer]                                                      gelatin                0.7       g/m.sup.2                                    5-nitroindazole        5         mg/m.sup.2                                   lipoic acid            8         mg/m.sup.2                                   C.sub.2 H.sub.5 SO.sub.2 Na                                                                          6         mg/m.sup.2                                   hydroquinone           50        mg/m.sup.2                                   1-hydroxy-2-benzaldoxime                                                                             15        mg/m.sup.2                                   latex polymer          (see Table 3)                                          [Upper Protective Layer]                                                      gelatin                0.5       g/m.sup.2                                    SiO.sub.2  fine particles (average particle size:                                                    55        mg/m.sup.2                                   (3.5 μm)                                                                   colloidal silica (average particle size:                                                             135       mg/m.sup.2                                   0.02 μm)                                                                   sodium dodecylbenzenesulfonate                                                                       25        mg/m.sup.2                                   Na salt of polyoxyethylene nonylphenyl ether                                                         20        mg/m.sup.2                                   sulfuric acid ester (degree of polymerization: 5)                             K salt of N-perfluorooctanesulfonyl-N-propyl-                                                        3         mg/m.sup.2                                   glycine                                                                       ______________________________________                                    

After the resulting samples were stored in an atmosphere of 25° C., 50%RH over one week, they were inspected for the following properties.

1) Sensitivity and γ Value

Each sample was exposed to light through an optical wedge using BrightRoom Printer P-627FM (light source: mercury lamp) and then processedunder developing conditions of a temperature of 38° C. and a developingtime of 20 seconds using SR-D2 and GR-F1 available from Fuji Photo FilmCo., Ltd. as the developer and fixing solution respectively andAutomatic Developing Machine FG-680AG (available from Fuji Photo FilmCo., Ltd.).

The sensitivity of each sample was determined in terms of a logarithmicnumber of the exposure value required for achieving the density of 3.0relative to that observed for Sample No. 15 which was assumed to be 100.

The γ value represents an average gradient of the characteristic curvewithin the density ranging from 0.3 to 3.0 and is expressed in terms ofa value obtained by dividing 2.7 by Δ logE (the difference between thelogarithmic number of the exposure value required for achieving thedensity of 3.0 and that required for achieving the density of 0.3). Thehigher the γ value, the higher the contrast of the resulting image.

2) Wet Film Strength

Each sample was immersed in distilled water maintained at 25° C. for 5minutes, a sapphire needle having a radius of 0.3 mm was attached to thesample film surface under pressure, followed by continuously increasingthe load applied to the needle while moving the needle at a speed of 10mm/sec to determine the load (g) required for breaking the film.

3) Brittleness

After each sample was allowed to stand in an atmosphere of 25° C., 10%RH for 2 hours, an average of the points at which crack was initiallyformed on the side of the silver halide emulsion layer was determined bythe same method defined in ISO6077 "Wedge Brittleness Test".

The results thus obtained are listed in the following Table 3. The datalisted in Table 3 clearly indicate that the samples of the presentinvention exhibit excellent photographic properties, are considerablyimproved in the wet film strength and good brittleness although theamount of the active methylene monomer used is small. Moreover, the sameexcellent results were also obtained when the total amounts of gelatinpresent in the emulsion layer and the protective layers are controlledto 3 g and 4 g respectively.

                  TABLE 3                                                         ______________________________________                                        Sam- Emulsion Layer    Lower Protective Layer                                 ple  Latex        Added    Latex      Added                                   No.  Polymer      Amount   Polymer    Amount                                  ______________________________________                                        1    P-3          0.85(g/m.sup.2)                                                                        P-3        0.35(g/m.sup.2)                         2    P-4          0.85     P-4        0.35                                    3    P-10         0.85     P-10       0.35                                    4    P-11         0.85     P-11       0.35                                    5    P-12         0.85     P-12       0.35                                    6    P-36         0.85     P-36       0.35                                    7    P-21         0.85     P-21       0.35                                    8    P-41         0.85     P-41       0.35                                    9    P-47         0.85     P-47       0.35                                    10   P-51         0.85     P-51       0.35                                    11   P-54         0.85     P-54       0.35                                    12   P-63         0.85     P-63       0.35                                    13   Comp. Compound 1                                                                           0.85     Comp. Compound 1                                                                         0.35                                    14   Comp. Compound 2                                                                           0.85     Comp. Compound 2                                                                         0.35                                    15   Comp. Compound 3                                                                           0.85     Comp. Compound 3                                                                         0.35                                    16   Comp. Compound 4                                                                           0.85     Comp. Compound 4                                                                         0.35                                    17   Comp. Compound 5                                                                           0.85     Comp. Compound 5                                                                         0.35                                    18   --           --       --         --                                      ______________________________________                                        Sample  Relative γ    Wet Film                                                                             Brittle-                                   No.     Sensitivity                                                                            Value      Strength                                                                             ness                                       ______________________________________                                        1       100      9          200(g) 2(mm)                                      2       100      9          220    2                                          3       100      9          220    2                                          4       98       9          210    2                                          5       102      9          210    2                                          6       100      9          215    2                                          7       98       9          210    2                                          8       102      9          170    2                                          9       100      9          165    2                                          10      100      9          170    2                                          11      100      9          160    2                                          12      100      9          170    2                                          13      100      9          60     2                                          14      98       9          85     10                                         15      100      9          120    3                                          16      102      9          130    2                                          17      100      9          110    12                                         18      100      9          190    13                                         ______________________________________                                         Comp. Compound 1: ethyl acrylate (100 (% by weiqht))                          Comp. Compound 2: ethyl acrylate/methyl methacrylate/styrene (50/15/35)       Comp. Compound 3: methl acrylate/2acrylamido-2-methylpro-panoic               acid/2acetoacetoxyethyl methacrylate (88/5/7)                                 Comp. Compound 4: ethyl acrylate/acrylic acid/2acetoaceto-xyethyl             methacrylate (86/4/16)                                                        Comp. Compound 5 (Polymer coupler disclosed in J.P. KOKAI No. Sho 5842044     core: poly(nbutyl acrylate)                                                   shell:                                                                        ##STR10##                                                                     core/shell = 9.1/90.9 (by weight)                                        

EXAMPLE 8

A conductive layer and a backing layer each having the followingcomposition were simultaneously coated on one side of a biaxiallyoriented polyethylene terephthalate substrate (thickness: 100 μm)provided with undercoating layers on both sides thereof.

    ______________________________________                                        [Conductive Layer]                                                            SnO.sub.2 /Sb (9/1 (weight ratio); average particle                                                   200    mg/m.sup.2                                     size: 0.25 μ)                                                              gelatin (Ca.sup.++  content: 3000 ppm)                                                                77     mg/m.sup.2                                     Compound-(1)            7      mg/m.sup.2                                     sodium dodecylbenzenesulfonate                                                                        10     mg/m.sup.2                                     sodium dihexyl-α-sulfosuccinate                                                                 40     mg/m.sup.2                                     sodium polystyrenesulfonate                                                                           9      mg/m.sup.2                                     ______________________________________                                    

The surface resistivity of the conductive layer as determined at 25° C.,20% RH was found to be 3.0×10⁹ Ω.

    ______________________________________                                        [Backing Layer]                                                               ______________________________________                                        gelatin (Ca.sup.++   content: 30 ppm)                                                                 2.82   g/m.sup.2                                      Compound-(1)            3      mg/m.sup.2                                     poly(methyl methacrylate) fine particles                                                              50     mg/m.sup.2                                     (average particle size: 3.4 μm)                                            Compound-(2)            40     mg/m.sup.2                                     Compound-(3)            40     mg/m.sup.2                                     Compound-(4)            80     mg/m.sup.2                                     Na dodecylbenzenesulfonate                                                                            75     mg/m.sup.2                                     Na dihexyl-α-sulfosuccinate                                                                     20     mg/m.sup.2                                     Compound-(5)            5      mg/m.sup.2                                     K N-perfluorooctanesulfonyl-N-propyl glycine                                                          7      mg/m.sup.2                                     sodium sulfate          50     mg/m.sup.2                                     sodium acetate          85     mg/m.sup.2                                     1,2-bis (vinylsulfonylacetamide)ethane                                                                150    mg/m.sup.2                                     ______________________________________                                        Compound-(1)                                                                   ##STR11##                                                                    Compound-(2)                                                                   ##STR12##                                                                    Compound-(3)                                                                   ##STR13##                                                                    Compound-(4)                                                                   ##STR14##                                                                    Compound-(5)                                                                  C.sub.8 F.sub.17 SO.sub.3 Li                                              

Then the following emulsion layer and upper and lower protective layerseach having the composition given below were simultaneously coated onthe opposite face of the substrate.

    ______________________________________                                        [Emulsion Layer]: Preparation of Emulsion                                     ______________________________________                                        Liquid I:                                                                     water                      1000   ml                                          gelatin                    20     g                                           sodium chloride            20     g                                           sodium 1,3-dimethylimidazolidine-2-thion                                                                 20     g                                           sodium benzenesulfonate    6      mg                                          Liquid II:                                                                    water                      400    ml                                          silver nitrate             100    g                                           Liquid III                                                                    water                      400    ml                                          sodium chloride            30.5   g                                           potassium bromide          14     g                                           potassium hexachloroiridate (III) (0.001% aq. soln.)                                                     15     ml                                          ammonium hexabromorhodate (III) (0.001% aq. soln.)                                                       1.5    ml                                          ______________________________________                                    

To Liquid I maintained at 38° C. and a pH of 4.5, there weresimultaneously added Liquid II and Liquid III over 10 minutes withstirring to give fine particles having a particle size of 0.16 μm. Thenthe following Liquid IV and Liquid V were added to the reaction systemover 10 minutes. Further 0.15 g of potassium iodide was added to themixture to finish the formation of grains.

    ______________________________________                                        Liquid IV:                                                                    water             400      ml                                                 silver nitrate    100      g                                                  Liquid V:                                                                     water             400      ml                                                 sodium chloride   30.5     g                                                  potassium bromide 14       g                                                  K.sub.4 Fe(CN).sub.6                                                                            1 × 10.sup.-5                                                                    mole/mole Ag                                       ______________________________________                                    

Thereafter the product was treated by the usual method, i.e., washed bythe flocculation method and then 40 g of gelatin was added.

The pH and pAg values of the resulting emulsion were adjusted to 5.3 and7.5 respectively, followed by addition of 5.2 mg of sodium thiosulfate,10.0 mg of chloroauric acid and 2.0 mg of N,N-dimethylselenoureathereto, addition of 8 mg of sodium benzenesulfonate, 2.0 mg of sodiumbenzenesulfonate, chemical sensitization such that the optimumsensitivity was attained at 55° C. to thus finally give an enulsioncomprising silver iodochlorobromide cubic grains which comprised 80 mole% of silver chloride and had an average particle size of 0.20 μm.

Then the following sensitizing dye 1 was added in an amount of 100 mgper mole of Ag to thus panchromatically sensitize the emulsion.Moreover, there were added, to the emulsion, hydroquinone and1-phenyl-5-mercaptotetrazole as antifoggants in amounts of 2.5 g and 50mg per mole of Ag respectively, colloidal silica (Snow Tex C availablefrom Nissan Chemical Industries, Ltd.; average particle size: 0.015 μm)in an amount of 30% by weight based on the amount of gelatin, a latexpolymer (the amounts and kinds are listed in the following Table 4) as aplasticizer and 100 mg/m² of 1,1'-bis(vinylsulfonyl)methane as afilm-hardening agent.

The resulting coating liquid was applied to the substrate in such anamount that the coated amounts of Ag and gelatin were 3.3 g/m² and 1.5g/m², respectively.

    __________________________________________________________________________    Sensitizing dye 1                                                              ##STR15##                                                                    __________________________________________________________________________    [Formulation of Lower Protective Layer]                                       gelatin                    0.5                                                                              g/m.sup.2                                       sodium benzenesulfonate    4  mg/m.sup.2                                      1,5-dihydroxy-2-benzaldoxime                                                                             25 mg/m.sup.2                                      latex polymer              (see Table 4)                                      [Formulation of Upper Protective Layer]                                       gelatin                    0.25                                                                             g/m.sup.2                                       poly(methyl methacrylate) fine particles                                                                 40 mg/m.sup.2                                      (average particle size: 2.7 μm)                                            Compound-(6) (dispersion of slippinq agent in gelatin)                                                   30 mg/m.sup.2                                      colloidal silica (Snow Tex C available from                                                              30 mg/m.sup.2                                      Nissan Chemical Industries, Ltd.)                                             Compound-(7)               5  mg/m.sup.2                                      sodium dodecylbenzenesulfonate                                                                           22 mg/m.sup.2                                      __________________________________________________________________________     Compound-(6)                                                                  ##STR16##                                                                     Compound(7)                                                                   C.sub.8 F.sub.17 SO.sub.2 N(C.sub.3 H.sub.7)--CH.sub.2 COOK              

The resulting samples each was exposed to xenon flash light having anemission time of 10⁻⁶ sec through an interference filter having a peakat 633 nm and a continuous density wedge, then developed using anautomatic developing machine FG-680AS available from Fuji Photo FilmCo., Ltd. and inspected for the sensitivity and the γ value in the samemanner used in Example 7.

The development was carried out at 38° C. for 11 seconds using SR-D2 andSR-F1 available from Fuji Photo Film Co., Ltd. as the developer and thefixing solution.

The determination of the wet film strength and the brittleness of eachsample was performed in the same manner used in Example 7.

The results thus obtained are listed in the following Table 4. As seenfrom the results listed in Table 4, the samples of the present inventiondo not show any reduction in the wet film strength even when the contentof the latex polymer is increased and exhibit very excellent quality.

                  TABLE 4                                                         ______________________________________                                        Sam- Emulsion Layer     Lower Protective Layer                                ple  Latex        Added     Latex      Added                                  No.  Polymer      Amount    Polymer    Amount                                 ______________________________________                                        19   P-4          0.37 (g/m.sup.2)                                                                        P-4        0.25                                                                          (g/m.sup.2)                            20   P-4          0.75      P-4        0.25                                   21   P-4          1.50      P-4        0.25                                   22   P-4          2.00      P-4        0.25                                   23   P-10         0.37      P-10       0.25                                   24   P-10         0.75      P-10       0.25                                   25   P-10         1.50      P-10       0.25                                   26   P-10         2.00      P-10       0.25                                   27   P-18         0.37      P-18       0.25                                   28   P-18         0.75      P-18       0.25                                   29   P-18         1.50      P-18       0.25                                   30   P-18         2.00      P-18       0.25                                   31   Comp. Compound 4                                                                           0.75      Comp. Compound 4                                                                         0.25                                   32   Comp. Compound 4                                                                           1.50      Comp. Compound 4                                                                         0.25                                   33   --           --        --         --                                     ______________________________________                                        Sam-                                                                          ple  Relative     γ   Wet Film   Brittle-                               No.  Sensitivity* Value     Strength   ness                                   ______________________________________                                        19   100          7         170 (g)    3 (mm)                                 20   100          7         175        2                                      21   100          7         170        2                                      22   100          7         170        2                                      23   100          7         168        3                                      24   100          7         170        2                                      25   100          7         170        2                                      26   100          7         170        2                                      27   100          7         175        3                                      28   100          7         170        2                                      29   100          7         170        2                                      30   100          7         165        2                                      31   100          7         110        3                                      32   100          7          90        2                                      33   100          7         170        14                                     ______________________________________                                         *The value relative to that observed for Sample No. 33 which is assumed t     be 100.                                                                  

EXAMPLE 9

The latex polymer compound P-4 of the present invention was substitutedfor the latex polymer in the emulsion layer and the lower protectivelayer used in Example 1 disclosed in J.P. KOKAI No. Hei 4-340951; thelatex polymer present in the backing layer, the first and secondemulsion layers and the lower protective layer used in Example 2, thelatex polymer present in the light-insensitive layer and the emulsionlayer used in Example 6, the latex polymer present in the UL layer, EMlayer and PC layer used in Example 7, the latex polymer present in theemulsion layer used in Example 8, the latex polymer present in thelowermost layer, first emulsion layer, intermediate layer and secondemulsion layer used in Example 11 disclosed in J.P. KOKAI No. Hei7-234478; and the latex polymer present in the emulsion layer used inExample 1 disclosed in J.P. KOKAI No. Hei 6-27590, and the resultinglight-sensitive materials were evaluated in the same manner used inExample 7 and it was found that the materials exhibited excellent filmcharacteristic properties while holding the photographic properties.

EXAMPLE 10

The same effects observed in Examples 7 and 8 of the present inventioncould be achieved when preparing coating samples according to Examples 1and 2 of J.P. KOKAI No. Hei 6-167781 and subjecting them to the sametreatments.

EXAMPLE 11

The same effects observed in Examples 7 and 8 of the present inventioncould be achieved when preparing coating samples according to Examples1, 2 and 3 of J.P. KOKAI No. Hei 6-250314 and subjecting them to thesame treatments.

EXAMPLE 12 Emulsion-A

To a 1.5% gelatin aqueous solution, maintained at 40° C. having a pH of2.0 and containing sodium chloride and sodium benzenethiosulfonate in anamount of 3×10⁻⁵ mole per mole of silver, there were simultaneouslyadded an aqueous solution of silver nitrate and an aqueous sodiumchloride solution containing (NH₄)Rh(H₂ O)Cl₅ in an amount of 3.5×10⁻⁵mole per mole of silver by the double-jet method at a voltage of 95 mVfor 3 minutes and 30 seconds so that the amount of the silver was a halfof the final amount of silver to prepare core particles having aparticle size of 0.12 μm. Thereafter an aqueous solution of silvernitrate and an aqueous sodium chloride solution containing (NH₄)₂ Rh(H₂O)Cl₅ in an amount of 10.5×10⁻⁵ mole per mole of silver were addedthereto over 7 minutes in the same manner used above to give silverhalide cubic grains having an average gain size of 0.15 μm (coefficientof variation: 12%).

Then 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene was added to theresulting emulsion in an amount of 1.5×10⁻⁵ mole per mole of silver.

Thereafter the product was washed with water by the flocculation methodwell-known in this art to remove the soluble salts, followed by additionof gelatin, and addition of 50 mg (per mole of silver) each ofCompound-A and phenoxyethanol as preservatives and4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene in an amount of 3.0'10⁻³ moleper mole of silver, without carrying out any chemical ripening (in thefinal grains, pH 5.7; pAg 7.5; Rh 7×10⁻⁵ mole/mole Ag).

[Preparation of Coating Solution for Emulsion Layer and ApplicationThereof]

The following compounds were added to the resulting emulsion and thecoating solution was applied to the following substrate provided with anundercoating layer such that the coated amount of gelatin was 1.1 g/m²and that of silver was 2.5 g/m² to give a silver halide emulsion layer.

    ______________________________________                                        4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene                                                          10       mg/m.sup.2                                      sodium salt of N-oleyl-N-methyl taurine                                                            35       mg/m.sup.2                                      Compound-B           10       mg/m.sup.2                                      Compound-C           20       mg/m.sup.2                                      Compound-D (film-hardening agent)                                                                  150      mg/m.sup.2                                      Compound-E (hydrazine derivative)                                                                  1.9 × 10.sup.-3                                                                  mole/mole Ag                                    Compound-F (nucleation accelerator)                                                                1.7 × 10.sup.-3                                                                  mole/mole Ag                                    ______________________________________                                    

Moreover, the latex polymer of the present invention was added (thekinds and amounts are summarized in the following Table 6).

Upper and lower emulsion protective layers were coated on the emulsionlayer.

[Preparation of Coating Solution for Lower Emulsion Protective Layer andApplication Thereof]

The following compounds were added to a gelatin aqueous solution and theresulting solution was coated such that the coated amount of gelatin was0.7 g/m².

    ______________________________________                                        gelatin (Ca.sup.++  content: 2700 ppm)                                                                0.7   g/m.sup.2                                       Compound-A              5     mg/m.sup.2                                      Compound-G              10    mg/m.sup.2                                      Compound-H              20    mg/m.sup.2                                      ______________________________________                                    

[Preparation of Coating Solution for Upper Emulsion Protective Layer andApplication Thereof]

The following compounds were added to a gelatin aqueous solution and theresulting solution was coated such that the coated amount of gelatin was0.8 g/m².

    ______________________________________                                        gelatin (Ca.sup.++  content: 2700 ppm)                                                                 0.8    g/m.sup.2                                     amorphous silica matting agent (average particle                                                       10     mg/m.sup.2                                    size: 2.5 μm; fine pore diameter: 17 nm;                                   surface area: 300 m.sup.2)                                                    K N-perfluorooctanesulfonyl-N-propyl glycine                                                           5      mg/m.sup.2                                    Na dodecylbenzenesulfonate                                                                             30     mg/m.sup.2                                    Compound-A               5      mg/m.sup.2                                    solid dispersed dye-I    100    mg/m.sup.2                                    solid dispersed dye-J    50     mg/m.sup.2                                    ______________________________________                                    

Then the following conductive layer and backing layer weresimultaneously coated on the opposite face of the substrate.

[Preparation of Coating Solution for Conductive Layer and ApplicationThereof]

The following compounds were added to a gelatin aqueous solution and theresulting solution was coated such that the coated amount of gelatin was77 mg/m².

    ______________________________________                                        SnO.sub.2 /Sb(9/1 (weight ratio); average particle                                                   200 mg/m.sup.2                                         size: 0.25 μm                                                              gelatin (Ca.sup.++  content: 3000 ppm)                                                               77 mg/m.sup.2                                          Na dodecylbenzenesulfonate                                                                           10 mg/m.sup.2                                          Na dihexyl-α-sulfosuccinate                                                                    40 mg/m.sup.2                                          Na polystyrenesulfonate                                                                               9 mg/m.sup.2                                          Compound-A              7 mg/m.sup.2                                          ______________________________________                                    

[Preparation of Coating Solution for Backing Layer and ApplicationThereof]

The following compounds were added to a gelatin aqueous solution and theresulting solution was coated such that the coated amount of gelatin was2.92 g/m².

    ______________________________________                                        gelatin (Ca.sup.++  content: 30 ppm)                                                                   2.92   g/m.sup.2                                     poly(methyl methacrylate) fine particles                                                               54     mg/m.sup.2                                    (average particle size: 3.4μ)                                              Compound-K               140    mg/m.sup.2                                    Compound-L               140    mg/m.sup.2                                    Compound-M               40     mg/m.sup.2                                    Na dodecylbenzenesulfonate                                                                             75     mg/m.sup.2                                    Na dihexyl-α-sulfosuccinate                                                                      20     mg/m.sup.2                                    Compound-N               5      mg/m.sup.2                                    K N-perfluorooctanesulfonyl-N-propyl glycine                                                           5      mg/m.sup.2                                    sodium sulfate           50     mg/m.sup.2                                    sodium acetate           85     mg/m.sup.2                                    ______________________________________                                    

[Substrate and Undercoating Layer]

First and second undercoating layers each having the followingcomposition were applied to both side of a binary oriented polyethyleneterephthalate substrate (thickness: 100 μm).

    ______________________________________                                        [First Undercoating Layer]                                                    ______________________________________                                        core/shell type vinylidene chloride copolymer 1                                                         15      g                                           2,4-dichloro-6-hydroxy-S-triazine                                                                       0.25    g                                           polyethylene fine particles (average particle                                                           0.05    g                                           size: 3μ                                                                   Compound-O                0.20    g                                           colloidal silica (Snow Tex ZL: particle size: 70                                                        0.12    g                                           to 100μ; available from Nissan Chemical                                    Industries, Ltd.)                                                             water                     ad. 100 g                                           ______________________________________                                    

Moreover, 10% by weight KOH was added to control the pH value to 6 andthe resulting coating solution was applied such that the thickness ofthe resulting dried film (drying temp. 180° C. for 2 minutes) was 0.9μ.

    ______________________________________                                        [Second Undercoating Layer]                                                   ______________________________________                                        gelatin               1        g                                              methyl cellulose      0.05     g                                              Compound-P            0.02     g                                              C.sub.12 H.sub.25 O(CH.sub.2 CH.sub.2 O).sub.10 H                                                   0.03     g                                              Compound-A            3.5 × 10.sup.-3                                                                  g                                              acetic acid           0.2      g                                              water                 ad. 100  g                                              ______________________________________                                    

The coating solution was applied such that the dried film thickness(drying temp. 170° C. for 2 minutes) was 0.1μ.

Samples 1 to 19 were prepared in the same manner used above. ##STR17##

Developers each having the formulation detailed in the following Table 5were prepared.

                  TABLE 5                                                         ______________________________________                                                       Developer No. & Composition                                    Developer Components                                                                           D-1*    D-2     D-3   D-4*                                   ______________________________________                                        potassium hydroxide                                                                            35 (g)  35 (g)  35 (g)                                                                              35 (g)                                 diethylenetriaminepentaacetic acid                                                             2.0     2.0     2.0   2.0                                    potassium carbonate                                                                            40      100     85    70                                     potassium bromide                                                                              3       3       3     3                                      5-methylbenzotriazole                                                                          0.08    0.08    0.08  0.08                                   Na 2-mercaptobenzimidazole-5-                                                                  0.15    0.15    0.15  0.15                                   sulfonate                                                                     2,3,5,6,7,8-hexahydro-2-dioxo-4-                                                               0.03    0.03    0.03  0.03                                   (1H)-quinazoline                                                              sodium metabisulfite                                                                           44      54      62    44                                     4-hydroxymethyl-4-methyl-1-                                                                    0.45    0.45    0.45  0.45                                   phenyl-3-pyrazolidone                                                         hydroquinone     23.3    30.0    35.0  23.3                                   sodium erythorbate                                                                             3.0     3.0     3.0   3.0                                    water            (ad. one liter)                                              pH               10.5    10.5    10.5  10.5                                   pH increase when 0.1 mole of                                                                   0.5     0.23    0.24  0.3                                    NaOH was added to one liter of                                                developer                                                                     ______________________________________                                         *Comparative Example                                                     

The formulation of the fixing solution used in the invention was asfollows.

    ______________________________________                                        [Formulation of Fixing Solution]                                              ______________________________________                                        ammonium thiosulfate     360    g                                             2Na ethylenediaminetetraacetate · 2 H.sub.2 O                                                 2.3    g                                             sodium thiosulfate · 5 H.sub.2 O                                                              33.0   g                                             sodium sulfite           75.0   g                                             sodium hydroxide         37.0   g                                             glacial acetic acid      87.0   g                                             tartaric acid            8.8    g                                             sodium gluconate         6.6    g                                             aluminum sulfate         25.0   g                                             water                    ad. 3  liter                                         pH (adjusted by addition of H.sub.2 SO.sub.4 or NaOH)                                                  4.85                                                 ______________________________________                                    

[Evaluation]

Each sample thus applied to the substrate was exposed to light throughan optical wedge using P-627FM Printer available from Dainippon ScreenCo., Ltd. and then subjected to a running test using an automaticdeveloping machine FG-680A available from Fuji Photo Film Co., Ltd. Therunning test comprised 6 rounds each comprising running for 6 days andrest for one day. In the operation, the film A of a large paper sheet(50.8 cm×60.1 cm) was processed in a rate of 40 sheets per day. In thetest, the amount of the developer supplemented was 180 ml/m², thedeveloping time was 30 seconds and the developing temperature was set at35° C.

These samples each was inspected for the following properties:

1) Sensitivity (S1.5): the logarithmic value of exposure required forachieving a density of 1.5 (the smaller the value, the higher thesensitivity).

2) γ value: (1.5-0.1)/{log(exposure required for achieving a density of1.5)-log(exposure required for achieving a density of 0.1}

3) Contamination with Silver: Each sample was visually observed andevaluated according to 5 stage-evaluation criteria. The condition inwhich the film, the developing tank and the rollers are not contaminatedwith silver is rated to be "5", while the condition in which the wholesurface of the film is contaminated with silver and the developing tankand the rollers are severely contaminated with silver is rated to be"1". The rank "4" means that the film is not contaminated, but thedeveloping tank and the rollers are slightly contaminated to apractically acceptable level. The rank "3" or lower is accompanied byproblems practically unacceptable or cannot practically be acceptable.

The results of photographic quality thus examined are summarized in thefollowing Table 6.

                                      TABLE 6                                     __________________________________________________________________________                                     Photographic Quality                                                                        Contami-                                                                           Remaining                 Exp.                                                                             Sample        Latex Polymer   Fresh Liquid                                                                        Fatigued Liquid                                                                       nation                                                                             Color                     No.                                                                              No. Developer                                                                          Emulsion                                                                           Compound                                                                            Added Amount(g/m.sup.2)                                                                 S.sub.1·5                                                               γ                                                                          S.sub.1·5                                                                γ                                                                           with Ag                                                                            Stain                     __________________________________________________________________________    1* 1   D-1  B    --    --        1.00                                                                             22.5                                                                             0.93                                                                              11.3                                                                              2    5                         2* 1   D-2  B    --    --        1.00                                                                             21.8                                                                             0.94                                                                              12.0                                                                              3    3                         3* 1   D-3  B    --    --        1.00                                                                             21.7                                                                             0.94                                                                              11.3                                                                              3    3                         4* 1   D-4  B    --    --        1.00                                                                             22.0                                                                             0.93                                                                              11.7                                                                              2    3                         5* 2   D-1  B    P-4   0.5       1.01                                                                             21.9                                                                             0.99                                                                              19.3                                                                              2    5                         6  2   D-2  B    P-4   0.5       1.02                                                                             22.3                                                                             1.00                                                                              19.5                                                                              4    5                         7  2   D-3  B    P-4   0.5       1.01                                                                             22.9                                                                             1.01                                                                              20.0                                                                              4    5                         8* 2   D-4  B    P-4   0.5       1.01                                                                             22.0                                                                             1.00                                                                              19.7                                                                              2    3                         9* 3   D-1  C    P-4   0.5       1.02                                                                             21.3                                                                             1.01                                                                              19.0                                                                              2    5                         10 3   D-2  C    P-4   0.5       1.01                                                                             21.8                                                                             1.00                                                                              19.3                                                                              4    5                         11 3   D-3  C    P-4   0.5       1.01                                                                             21.9                                                                             0.99                                                                              19.5                                                                              4    5                         12*                                                                              3   D-4  C    P-4   0.5       1.02                                                                             22.2                                                                             1.00    2    3                         __________________________________________________________________________     *: Comparative Example                                                   

Experiment Nos. 6, 7, 10 and 11 corresponding to the image-formingmethod of the present invention exhibited only low variations in thesensitivity and the γ value observed during the running test and thesesamples were only slightly contaminated with silver.

EXAMPLE 13 Emulsion-B

To an aqueous gelatin solution containing sodium chloride and1,3-dimethyl-2-imidazolinethion, there were simultaneously added a 0.37mole aqueous solution of silver nitrate and an aqueous halide saltsolution containing (NH₄)₃ RhCl₆, KIrCl₆, potassium bromide and sodiumchloride in amounts of 1.0×10⁻⁷ mole, 2×10⁷ mole, 0.11 mole and 0.27mole per mole of silver in the final emulsion, respectively at 45° C.for 12 minutes with stirring using the double jet method to form silverchlorobromide particles having an average particle size of 0.20 μm and asilver chloride content of 70 mole % and to thus perform nucleation.Then a 0.63 mole aqueous silver nitrate solution and an aqueous halidesolution containing 0.19 mole of potassium bromide and 0.47 mole ofsodium chloride were likewise added thereto over 20 minutes using thedouble jet method. Thereafter, a KI solution having a concentration of1×10⁻³ mole per mole of silver was added to perform conversion followedby water-washing by flocculation according to the usual method, additionof 40 g of gelatin, control of pH and pAg to 6.5 and 7.5 respectively,addition of sodium benzenethiosulfonate, sodium thiosulfate andchloroauric acid in amounts of 7 mg, 5 mg and 8 mg per mole of silver,heating at 60° C. for 45 minutes, subjecting the emulsion to chemicalsensitization and addition of 150 mg of4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene as a stabilizer and Proxel asa preservative. The resulting particles were silver chlorobromide cubicgrains having an average particle size of 0.28 μm and a silver chloridecontent of 70 mole % (coefficient of variation: 9%).

Emulsion-C

To Liquid 1 listed in Table 2 maintained at 38° C. and a pH of 4.5,there were simultaneously added Liquid 2 and Liquid 3 with stirring over24 minutes to form particles having a particle size of 0.18 μm.Subsequently, Liquid 4 and Liquid 5 listed in Table 1 were added over 8minutes, followed by addition of 0.15 g of potassium iodide to thuscomplete the particle-formation.

Then the particles were washed with water by flocculation according tothe usual method, followed by addition of gelatin, control of pH and pAgto 5.2 and 7.5 respectively, addition of 4 mg of sodium thiosulfate, 2mg of N,N-dimethylselenourea, 10 mg of chloroauric acid, 4 mg of sodiumbenzenethiosulfonate and 1 mg of sodium benzenethiosulfinate andchemical sensitization such that the emulsion exhibited optimumsensitivity at 55° C. Further, 50 mg of2-methyl-4-hydroxy-1,3,3a,7-tetrazaindene as a stabilizer was added andphenoxyethanol as a preservative was added to a concentration of 100 ppmto thus finally give silver iodochlorobromide cubic grains having asilver chloride content of 80 mole % and an average particle size of0.20 μm (coefficient of variation: 9%).

Coating solutions were applied to a substrate of a polyethyleneterephthalate film (150 μm) provided with an undercoating layer (0.5 μm)of a vinylidene chloride copolymer in such a layer structure that UL,EM, ML and PC were arranged in this order from the side of thesubstrate. The method for preparing each layer and the coated amountthereof will be detailed below.

(UL)

To 10 g of gelatin, there were added, based on the amount of gelatin, 50wt % of polyethyl acrylate latex and 3.5 wt % of compound (i) followedby addition of water in an amount such that the final volume was equalto 250 ml. This coating solution was applied such that the coated amountof gelatin was 0.4 g/m².

(EM)

The foregoing emulsions B and C were dissolved together with gelatin at40° C., followed by addition of 3.2×10⁻⁴ mole/mole Ag of a sensitizingdye compound (i), 2.7×10⁻⁴ mole/mole Ag of a sensitizing dye compound(ii), 3.4×10⁻³ mole/mole Ag of KBr, 3.2×10⁻⁴ mole/mole Ag of a compound(iii), 7.4×10⁻⁴ mole/mole Ag of a compound (iv), 9.7×10⁻³ mole/mole Agof hydroquinone, 8.0×10⁻³ mole/mole Ag of phosphoric acid, 4.5×10⁻⁴mole/mole Ag of a compound (v), 5.3×10⁻⁴ mole/mole Ag of a compound (vi)and 3×10⁻⁴ mole/mole Ag of a compound (vii), and addition of poly(ethylacrylate) in an amount of 15 wt % based on the amount of gelatin, thelatex polymer of the present invention as shown in Table 3 and acompound (viii) in an amount of 4 wt % based on the amount of gelatin togive a coating solution. The solution was applied such that the coatedamount of Ag was 3.3 g/m².

(ML)

To a gelatin solution, there were added 7 mg/m² of Compound F,poly(ethyl acrylate) in an amount of 15 wt % based on the amount ofgelatin and a compound (viii) in an amount of 3.5 wt % based on theamount of gelatin to give a coating solution. The solution was appliedsuch that the coated amount of gelatin was 0.5 g/m².

(PC)

To a gelatin solution, there were added 40 mg/m² of amorphous SiO₂matting agent having an average particle size of 3.5 μm, 20 mg/m² ofsilicone oil and 5 mg/m² of a compound (ix) and 25 mg/m² of sodiumdodecylbenzenesulfonate as coating aids to give a coating solution andthe solution was applied. The coated amount of gelatin was found to be0.3 g/m².

Additives for the Light-sensitive Material of Example 13 ##STR18##

Moreover, a backing layer and a back-protective layer having thefollowing formulations were coated.

    ______________________________________                                        [Backing Layer Formulation]                                                   ______________________________________                                        gelatin                 3       g/m.sup.2                                     latex: poly(ethyl acrylate)                                                                           2       g/m.sup.2                                     surfactant: sodium p-dodecylbenzenesulfonate                                                          40      mg/m.sup.2                                    compound (viii)         110     mg/m.sup.2                                    SiO.sub.2 /Sb(weight ratio: 90/10; average particle                                                   200     mg/m.sup.2                                    size: 0.20 μm)                                                             dye: mixture of dyes (a), (b) and (c)                                         dye (a)                 70      mg/m.sup.2                                    dye (b)                 100     mg/m.sup.2                                    dye (c)                 50      mg/m.sup.2                                    gelatin                 0.8     mg/m.sup.2                                    poly(methyl methacrylate) fine particles (average                                                     30      mg/m.sup.2                                    particle size: 4.5 μm)                                                     sodium dihexyl-α-sulfosuccinate                                                                 15      mg/m.sup.2                                    sodium p-dodecylbenzenesulfonate                                                                      15      mg/m.sup.2                                    sodium acetate          40      mg/m.sup.2                                    ______________________________________                                         Dye (a)                                                                       ##STR19##                                                                     Dye (b)                                                                       ##STR20##                                                                     Dye (c)                                                                       ##STR21##                                                                

Samples thus prepared each was exposed to light emitted from xenon flashlight rays having an emission time of 10⁻⁵ sec through an interferencefilter having a peak at 488 nm and a continuous wedge. Then theirphotographic properties in a fresh liquid and a fatigued liquid throughrunning were evaluated in the same manner used in Example 12. Inaddition to the properties evaluated in Example 12, they were alsoinspected for the remaining color stain by the following method.Remainin Color Stain:

Each film processed in a fresh developer was visually observed andevaluated according to 5 stage evaluation criteria. A film completelyfree of remaining color stain is rated to be "5" and a film exhibitingconsiderably high remaining color stain is rated to be "1". The rank "4"means that the film exhibits slight remaining color stain, but ispractically acceptable. The rank "3" or lower is accompanied by problemspractically unacceptable or can not practically be acceptable.

The results of photographic quality observed by the foregoing runningtests are summarized in the following Table 7.

                                      TABLE 7                                     __________________________________________________________________________                                Photographic Quality                              Exp.                                                                             Sample   Latex Polymer   Fresh Liquid                                                                        Fatigued Liquid                                                                       Contamination                       No.                                                                              No. Developer                                                                          Compound                                                                            Added Amount (g/m.sup.2)                                                                S.sub.1·5                                                               γ                                                                          S.sub.1·5                                                                γ                                                                           with Ag                             __________________________________________________________________________    13*                                                                              4   D-1  --    --        1.00                                                                             21.0                                                                             0.94                                                                              12.1                                                                              2                                   14*                                                                              4   D-2  --    --        1.00                                                                             20.8                                                                             0.93                                                                              19.1                                                                              3                                   15*                                                                              4   D-3  --    --        1.00                                                                             21.2                                                                             0.94                                                                              19.3                                                                              2                                   16*                                                                              4   D-4  --    --        1.00                                                                             22.0                                                                             0.95                                                                              11.5                                                                              2                                   17*                                                                              5   D-1  P-4   0.5       1.01                                                                             21.9                                                                             1.00                                                                              15.3                                                                              2                                   18 5   D-2  P-4   0.5       1.02                                                                             22.3                                                                             1.02                                                                              20.1                                                                              4                                   19 5   D-3  P-4   0.5       1.02                                                                             22.5                                                                             1.01                                                                              19.7                                                                              4                                   20*                                                                              5   D-4  P-4   0.5       1.02                                                                             20.9                                                                             1.01                                                                              14.3                                                                              2                                   21*                                                                              6   D-1  Q-1   0.5       1.02                                                                             21.7                                                                             1.01                                                                              16.0                                                                              2                                   22 6   D-2  Q-1   0.5       1.02                                                                             21.8                                                                             1.00                                                                              20.3                                                                              4                                   23 6   D-3  Q-1   0.5       1.03                                                                             22.1                                                                             1.01                                                                              19.3                                                                              4                                   24*                                                                              6   D-4  Q-1   0.5       1.02                                                                             21.3                                                                             1.00                                                                              15.2                                                                              2                                   __________________________________________________________________________     *: Comparative Example                                                   

Experiment Nos. 18, 19, 22 and 23 corresponding to the image-formingmethod of the present invention exhibited only low variations in thesensitivity and the γ value observed during the running test and thesesamples were only slightly contaminated with silver.

EXAMPLE 14

The same running tests used in Example 13 were performed except that thefollowing developers were substituted for the developer used in Example13 to thus evaluate the film-forming methods.

The developers were prepared from processing agents stored in solid andliquid conditions. The formulation of the developers used and thestorage conditions thereof are listed in the following Table 8.

The solid processing agent was prepared by packing solid developingagents in a bag comprising a plastic material coated with aluminum, inlayers. The solid agents were laminated in the following order from theside of the top layer.

    ______________________________________                                        first layer        hydroquinone                                               second layer       other components                                           third layer        sodium bisulfite                                           fourth layer       potassium carbonate                                        ______________________________________                                    

The bag was exhausted by the usual method and sealed under vacuum.

The liquid processing agent was stored in the form of a concentratehaving a formulation of 1.5 time (degree of dilution=2:1) that of theprocessing solution practically used.

The solid and liquid processing agents were used in the running testsafter storing at 50° C. for 60 days.

The development was carried out at 35° C. for 30 seconds. The fixingprocess was carried out at 37° C. using GR-F1 as a fixing solution whilesupplementing the fixing solution at a rate of 120 ml/m². The resultsobtained and conditions for experiments are summarized in the followingTable 9. The photographic properties were evaluated in the same mannerused in Example 13 and the uneven processing was evaluated by outputtinga 90% flat net at 100 lines to each sample using Color Scanner SG708equipped with an argon light source available from Dainippon Screen Co.,Ltd. and visually evaluating the degree of uneven processing. Theunevenness was rated according to 5-stage evaluation by sensory testing.In the evaluation of the uneven processing, each sample was processedafter completion of the running test.

                  TABLE 8                                                         ______________________________________                                                          Developer No. & Composition                                 Developer Components                                                                            D-5*    D-6*    D-7   D-8                                   ______________________________________                                        potassium hydroxide                                                                             35(g)   35(g)   35(g) 35(g)                                 diethylenetriaminepentaacetic acid                                                              2.0     2.0     2.0   2.0                                   potassium carbonate                                                                             40      40      100   100                                   potassium bromide 3       3       3     3                                     5-methylbenzotriazole                                                                           0.08    0.08    0.08  0.08                                  Na 2-mercaptobenzimidazole-5-                                                                   0.15    0.15    0.15  0.15                                  sulfonate                                                                     2,3,5,6,7,8-hexahydro-2-dioxo-4-                                                                0.03    0.03    0.03  0.03                                  (1H)-quinazoline                                                              sodium metabisulfite                                                                            44      44      54    54                                    4-hydroxymethyl-4-methyl-1-phenyl-                                                              0.45    0.45    0.45  0.45                                  3-pyrazolidone                                                                hydroquinone      23.3    23.3    30.0  30.0                                  sodium erythorbate                                                                              3.0     3.0     3.0   3.0                                   water             (ad. one liter)                                             pH                10.5    10.5    10.5  10.5                                  Storage Condition of Developer                                                                  liquid  solid   liquid                                                                              solid                                 pH increase when 0.1 mole of NaOH                                                               0.5     0.5     0.23  0.23                                  was added to one liter of                                                     developer                                                                     ______________________________________                                         *: Comparative Example                                                   

                                      TABLE 9                                     __________________________________________________________________________                                     Photographic Quality                                                                        Contami-                                                                           Uneven                    Exp.                                                                             Sample        Latex Polymer   Fresh Liquid                                                                        Fatigued Liquid                                                                       nation                                                                             Process-                  No.                                                                              No. Developer                                                                          Emulsion                                                                           Compound                                                                            Added Amount(g/m.sup.2)                                                                 S.sub.1·5                                                               γ                                                                          S.sub.1·5                                                                γ                                                                           with Ag                                                                            ing                       __________________________________________________________________________    25*                                                                              3   D-5  C    P-4   0.5       1.00                                                                             21.3                                                                             0.89                                                                              12.1                                                                              2    2                         26*                                                                              3   D-6  C    --    --        1.00                                                                             21.4                                                                             0.88                                                                              13.0                                                                              3    3                         27 3   D-7  C    --    --        1.00                                                                             21.5                                                                             0.95                                                                              19.8                                                                              4    4                         28 3   D-8  C    --    --        1.00                                                                             21.9                                                                             0.96                                                                              19.5                                                                              4    5                         __________________________________________________________________________     *: Comparative Example                                                   

Experiment Nos. 27 and 28 corresponding to the image-forming method ofthe present invention exhibited only low variations in the sensitivityand the γ value observed during the running test and these samplesshowed only slight contamination with silver and a low degree of unevenprocessing. In particular, in the image-forming method (Experiment No.28) which makes use of the developer D-8 prepared from a solidprocessing agent, the method is excellent in processing stability andfree of any uneven processing.

What is claimed is:
 1. A latex polymer of fine particles having aheterogeneous phase structure comprising a core consisting of a polymerhaving repeating units derived from a conjugated diene monomer and ashell consisting of a polymer having repeating units derived from atleast one ethylenically unsaturated monomer carrying an active methylenegroup.
 2. The latex polymer fine particles of claim 1 wherein the weightratio of the core polymer to the shell polymer ranges from 20/80 to95/5.
 3. The latex polymer fine particles of claim 1 wherein theethylenically unsaturated monomer carrying an active methylene group isa monomer represented by the following general formula (I):

    CH.sub.2 ═C(R.sup.1)--L--X

wherein R¹ represents a hydrogen atom, an alkyl group having 1 to 4carbon atoms or a halogen atom; L represents a single bond or a bivalentcoupling group; X represents an active methylene group selected from thegroup consisting of R² COCH₂ COO--, NC--CH₂ COO--, R² COCH₂ CO--,NC--CH₂ CO-- (wherein R² represents a substituted or unsubstituted alkylgroup having 1 to 12 carbon atoms, a substituted or unsubstituted arylor aryloxy group having 6 to 20 carbon atoms, an alkoxy group having 1to 12 carbon atoms, an amino group or a substituted amino group having 1to 12 carbon atoms) and R⁹ --CO--CH₂ CON(R⁶)-- (wherein R⁶ represents ahydrogen atom or a substituted or unsubstituted alkyl group having 1 to6 carbon atoms and R⁹ represents a substituted or unsubstituted, primaryor secondary alkyl group having 1 to 12 carbon atoms, an alkoxy grouphaving 1 to 12 carbon atoms, an amino group or a substituted amino grouphaving 1 to 12 carbon atoms), provided that if L is not a single bond, Lis bonded to X in the form of an alkylene, aralkylene or arylene.